Yeasts

Eur J Biochem, 1981 Apr, 115(3), 635 - 41
Conformational changes of yeast tRNAphe as monitored by 31P NMR; Salemink PJ et al.; The 31P NMR spectra of tRNAs contain approximately 17 resonances resolved from the main resonance which consists of about 80% of the total resonance intensity arising from the sugar phosphate backbone . In the present paper we study the behavior of the 31P resonances of yeast tRNAPhe as a function of temperature and of solution conditions . By comparison with other melting experiments we show that three resonances (called c, e and j2) belong to phosphates in the anticodon loop, while the remaining resolved 31P resonances come from phosphates in specific conformations in the central part of the molecule imposed by the tertiary structure . These conformations are different from the normal g-,g- conformation found in A-RNA double helices . The assignments are in good agreement with those previously made on the basis of chemical and enzymatic modification experiments {P . J . M . Salemink, T . Swarthof & C . W . Hilbers (1979) Biochemistry, 18, 3477-3485} . AT high Mg2+ concentrations the anticodon loop is found to be present in two different conformations . For all solution conditions studied loss of the anticodon loop structure takes place before the tertiary structure is melted out . The melting of the tertiary structure is not strictly an all- or-none process . The lifetimes of phosphate conformations involved in the tertiary structure may differ by at least a factor of two . It can also be concluded that the range of chemical shifts observed for phosphodiesters cannot at the moment be accounted for by theoretical calculations.

Proc Natl Acad Sci U S A, 1981 Apr, 78(4), 2244 - 8
Carbohydrate chains on yeast carboxypeptidase Y are phosphorylated; Hashimoto C et al.; Carboxypeptidase Y, a vacuolar enzyme from Saccharomyces cerevisiae, was digested with endo-beta-N-acetyl-D-glucosaminidase H to release the four oligosaccharide chains that are linked to asparagine in the glycoprotein . The oligosaccharides were fractionated into a neutral and acidic component, and the latter proved to phosphorylated . From its gel filtration pattern, the neutral fraction was shown to be a mixture of at least four homologs, the smallest of which had a proton NMR spectrum almost identical to that given by an IgM oligosaccharide with eight mannoses and one N-acetylglucosamine {Cohen, R . E . & Ballou, C . E . (1980) Biochemistry 19, 4345--4358} . The yeast oligosaccharide has one additional mannose unit in an alpha 1 leads to 3 or alpha 1 leads to 6 linkage, whereas the larger homologs appear to have two, three, and four more mannose units . One phosphorylated oligosaccharides with a mannose/phosphate ratio of 12.5 was reduced with NaB3H4 and then subjected to mild acid hydrolysis . This released mannose and mannobiose that were glycosidically linked to the phosphate group, whereas complete acid hydrolysis yielded D-mannose 6-phosphate . The recovered oligosaccharide phosphomonoester, which contained 11 or 12 mannose units, was digested exhaustively with alpha-mannosidase, and the product of this reaction was treated with alkaline phosphatase, which yielded radioactive Man3GlcNAcH2 . These results suggest that the mannosidase-resistant phosphorylated oligosaccharide has the structure Man leads to P leads to 6 alpha Man leads to alpha Man leads to 6 beta Man leads to 4GlcNAcH2, in which some of the phosphate groups are substituted with mannobiose instead of mannose . A second phosphorylated oligosaccharide with a mannose/phosphate ratio of 6.5 probably contains two phosphodiester groups, but its structure has not been investigated in detail.

Proc Natl Acad Sci U S A, 1981 Apr, 78(4), 2082 - 5
Molecular rulers for measuring RNA structure: sites of crosslinking in chlorambucilyl-phenylalanyl-tRNAPhe (yeast) and chlorambucilyl-pentadecaprolyl-phenylalanyl-tRNAPhe (yeast) intramolecularly crosslinked in aqueous solution; Wickstrom E et al.; Intramolecular crosslinking of yeast phenylalanine tRNA in aqueous solution with rigid, variable-length crosslinking reagents, which we call "molecular rulers," has given results in reasonable agreement with the crystal structure . Chlorambucilyl-{3H}phenylalanyl-tRNAPhe crosslinked intramolecularly at G-71 and A-73, whereas chlorambucilyl-pentadecaprolyl-{3H}phenylalanyl-tRNAPhe crosslinked at G-20 and Y-37 . The pentadecaprolyl reagent was predicted to be 62 A long, including chlorambucil and phenylalanine; the sites that it reached are 60 A distant from the 3' OH (in the case of G-20) or 80 A distant (in the case of Y-37) in the crystal structure of tRNAPhe . The close agreement between the length of the reagent and the distance of G-20 from the 3' OH in the crystal structure illustrates the rigidity of the tRNAPhe molecule in the dihydrouridine loop region at the corner of the molecule . The apparent ability of the 62-A-long reagent to crosslink to a site, Y-37, that is 80 A distant from the 3' OH in the crystal structure appears to illustrate the flexibility of both the 3' A-C-C-A terminus and the anticodon stem and loop, with respect to the tRNA molecule . These observations demonstrate the utility of oligoproline-based crosslinking reagents as rigid, variable-length molecular rulers for biological macromolecules in solution.

Biochim Biophys Acta, 1981 Mar 20, 642(1), 173 - 81
Factors affecting the inhibition of yeast plasma membrane ATPase by vanadate; Borst-Pauwels GW et al.; Inhibition of yeast plasma membrane ATPase by vanadate occurs only if either Mg2+ or MgATP2- is bound to the enzyme . The dissociation constant of the complex of vanadate and inhibitory sites is 0.14-0.20 microM in the presence of optimal concentrations of Mg2+ and of the order of 1 microM if the enzyme is saturated with MgATP2- . The dissociation constants of Mg2+ and MgATP2- for the sites involved are 0.4 and 0.62-0.73 mM, respectively, at pH 7 . KCl does not increase the affinity of vanadate to the inhibitory sites as was found with (Na+ + K+)-ATPase . On the other hand, the effect of Mg2+ upon vanadate binding is similar to that upon (Na+ + K+)-ATPase, and the corresponding affinity constants of Mg2+ and vanadate for the two enzymes are of the same order of magnitude.

Biochemistry, 1981 Mar 17, 20(6), 1653 - 9
Changes in the solution structure of yeast phenylalanine transfer ribonucleic acid associated with aminoacylation and magnesium binding; Potts RO et al.; The effect of aminoacylation on the structure of yeast phenylalanine tRNA was evaluated by laser light scattering . In these experiments, the translational diffusion coefficient (D20,w) of phenylalanyl-tRNA was monitored continuously during spontaneous deacylation in a variety of solution conditions . The results reveal that significant changes can occur in the hydrodynamic volume and electric charge as a consequence of aminoacylation but that the effects are magnesium dependent . At neutral pH, 20 degrees C, and 0.1 M salt, the D20,w value increased by 18% when deacylation occurred in 2--10 mM Mg2+ concentrations while no change in diffusivity was observed for tRNA deacylating in 0.5--1.0 mM Mg2+ . The Mg2+ concentration dependence of the D20,w changes behaves in highly cooperative manner . The electric charges of aminoacyl-tRNA and nonacylated tRNA in 1 and 10 mM Mg2+ were estimated from the diffusive virial coefficients . In the higher Mg2+ conditions, aminoacyl-tRNA has a charge of 15 +/- 2e- while that of the nonacylated form is 10 +/- 2e-; both acylated and nonacylated tRNA have a charge of 11 +/- 4e- in 1 mM Mg2+ . Taken together, the results indicate that aminoacylation permits the binding of additional Mg2+, resulting, in turn, in the formation of a more extended conformer of lower diffusivity and greater negative charge . The results also provide a possible explanation for several contradictory results in the literature.

Biochemistry, 1981 Mar 17, 20(6), 1513 - 20
Glutathione reductase from yeast . Differential reactivity of the nascent thiols in two-electron reduced enzyme and properties of a monoalkylated derivative; Arscott LD et al.; Two-electron reduced glutathione reductase from yeast reacted with iodoacetamide is alkylated almost exclusively in the nascent thiol nearer the amino terminus of the protein . The charge-transfer absorbance, maximal at 530 nm, characteristic of the two-electron reduced enzyme is not lost as the alkylation proceeds, and the product has a spectrum virtually identical with that of the two-electron reduced enzyme . This observation demonstrates that the thiol alkylated is not the charge-transfer-donor thiolate which interacts with the FAD . The spectrum of the monoalkylated derivative is stable in the presence of oxidized glutathione, indicating that the charge-transfer-donor thiol is not involved in interchange with the substrate in the native enzyme . Thus, the nascent thiols produced upon two-electron reduction of glutathione reductase have distinct functions, interchange with the substrate and interaction with the FAD . Treatment of the monoalkylated derivative with the apolar phenylmercuric acetate eliminates the charge-transfer interaction . The spectrum of the resulting species is similar to that of the oxidized enzyme but less resolved and blue shifted by 10 nm . The dependence on pH of the absorbance associated with the thiolate to FAD charge-transfer interaction in native two-electron reduced glutathione reductase is biphasic, with pK values at approximately 4.8 and 7.4 . By analogy with glyceraldehyde-3-phosphate dehydrogenase and papain, these data indicate that the thiolate is stabilized by an adjacent basic residue . The pK 7.4 is associated with the titration of the base to give the ion pair, and the pK of 4.8 is associated with the titration of the thiolate . Unlike lipoamide dehydrogenase, glutathione reductase is sufficiently stable to allow titration with dithionite at pH 3.7 . The spectrum at this pH is essentially the same as that of the monoalkylated derivative treated with phenylmercuric acetate . The changes with pH are completely reversible.

Biochim Biophys Acta, 1981 Mar 12, 635(1), 187 - 93
Hydrophobic photolabelling of the yeast cytochrome c oxidase subunits in contact with lipids; Gutweniger H et al.; The hydrophobic domain of the membrane-bound enzyme yeast cytochrome c oxidase was labelled with photoactivable phosphatidylcholines . Subunits I, II and III were labelled; a minor labelling was also found on subunits V and VII . The labelling of subunit V was located in a small terminal polypeptide sequence.

Biochemistry, 1981 Mar 3, 20(5), 1229 - 35
Liberation of the triosephosphate isomerase reaction intermediate and its trapping by isomerase, yeast aldolase, and methylglyoxal synthase; Iyengar R et al.; When a mixture of triosephosphate isomerase (rabbit muscle) and dihydroxyacetone phosphate (DHAP) is quenched with acid, a compound is liberated, presumed to be the cis-enediol 3-phosphate, that decomposes to inorganic phosphate (Pi) and methylglyoxal {Iyengar, R., & Rose, I.A . (1981) Biochemistry (preceding paper is this issue)} . The decomposition can be prevented by rapid neutralization if a catalytic amount of fresh isomerase is present . Varying the time between acidification and rescue gave a half-life of the liberate compound of approximately 12-17 ms . Varying the concentration of enzyme used for rescue gave a minimum second-order rate constant for trapping of 10(9)M(-1)s(-1) . These results add further evidence favoring a stepwise mechanism for the aldose-ketose isomerase reactions in which a chemically defined enzyme-bound intermediate is found . The high rate of trapping over a wide pH range indicates that the enediol phosphate, not the enediolate phosphate, is the intermediate . One property of the enzyme is to stabilize the intermediate with respect to its fragmentation in solution by greater than 1000-fold . Yeast aldolase is also able to rescue all of the isomerase intermediate, though higher concentrations of enzyme are required . Although different enantiotopic protons of DHAP are abstracted by isomerase and aldolase, both enzymes use the same enediol phosphate intermediate . Methylglyoxal synthase at a 50-fold greater concentration was unable to compete with triosephosphate isomerase for cis-enediol phosphate . Either the synthetase has a low V/K for the cis isomer or it uses the trans-enediol phosphate form specifically . A new strategy for the chemical and enzymological characterization of enzyme reaction intermediates is proved here based on the liberation of the intermediate from the reaction equilibrium and its recovery by fresh enzyme or another enzyme species.

Biochemistry, 1981 Mar 3, 20(5), 1147 - 56
Nuclear magnetic resonance and nuclear Overhauser effect study of yeast phenylalanine transfer ribonucleic acid imino protons; Johnston PD et al.; Results directed primarily toward spectral assignment and nuclear spin dynamics are described for yeast tRNAPhe in 0.1 M NaCl, pH 7 . Magnesium titrations were performed . Changes in the spectrum occur for Mg2+/tRNA ratios of about 2 and above 10 . Difference spectroscopy between 43 and 29 degrees C in zero Mg2+ concentration, together with prior identification of the GU4 acceptor stem base pair, indicates early acceptor melting and is used to identify acceptor resonances . Transport of spin energy (spin diffusion) is described in tRNA together with a summary of relevant experiments . A survey of nuclear Overhauser effects (NOE's) between imino and aromatic and amino protons is included, together with some recent conclusions based on methyl NOE's and experiments with tRNAs deuterated at the purine C8 position . Assignment of the imino NMR spectrum on the basis of these and previous data is reviewed and discussed in detail . Preliminary distance estimates based on the NOE for AU and GU4 base pairs are in reasonable agreement with the expected distances.

Int J Pept Protein Res, 1981 Mar, 17(3), 393 - 400
Structural studies on yeast 3-phosphoglycerate kinase . Linear arrangement of the CNBr fragments, partial amino acid sequence of the inner part of the polypeptide chain, and analyses of the N-terminal domain of the protein; Fattoum A et al.; The purpose of this work was to contribute to the study of the covalent structure of yeast 3-phosphoglycerate kinase . First, we undertook the complete alignment of the four fragments produced by cyanogen-bromide cleavage and which constitute the intact protein; we then established the total amino acid sequence of a 30-residue peptide and the N-terminal sequence of a 65-residue peptide . Second, we analyzed the acetylated state of the protein . The analyses of the acid fraction "P" obtained after digestion of 3-phosphoglycerate kinase by pronase enabled us to determine the N-terminal sequence of this enzyme as N-acetylserylglycine . Third, we isolated, purified and analyzed seven tryptic peptides from a fragment containing 102 amino acids coming from the N-terminal end of the protein . The peptides occupying the N- and C-terminal ends of this fragment were also identified.

Mutat Res, 1981 Mar, 81(1), 27 - 36
Light-flash analysis of the photoenzymic repair process in yeast cells . II . Determination of the rate constant for formation of photoreactivating enzymes-pyrimidine dimer complexes and its activation energy term; Fukui A et al.; As reported in the previous paper, the number of deoxyribodipyrimidine photolyase or photoreactivating enzyme (PRE) molecules per yeast cell was determined by the use of intense light flashes . In the present work, the reaction rate constant for the formation of PRE-substrate complexes, k1, and the activation energy term of k1 were determined by yeast cells in vivo by the use of light flashes . At 30 degrees C, k1 equalled (6.5 +/- 1.1) x 10(-5) (nuclear volume) x (molecule)(-1) sec(-1), which corresponded to 1.1 x 10(5) 1 mole(-1) sec(-1), on the assumption that a nuclear volume is 3 x 10(-15) 1 . k1 showed positive temperature dependence as described by the arrhenius expression with an activation energy of 11.8 +/- 1.6 kcal mole(-1).

Proc Natl Acad Sci U S A, 1981 Mar, 78(3), 1606 - 8
Conformational activation of the yeast phenylalanyl-tRNA synthetase catalytic site induced by tRNAPhe interaction: triggering of adenosine or CpCpA trinucleoside diphosphate aminoacylation upon binding of tRNAPhe lacking these residues; Renaud M et al.; Adenosine or CpCpA trinucleoside diphosphate can be aminoacylated by phenylalanyl-tRNA synthetase {L-phenylalanine:tRNAPhe ligase (AMP forming), EC 6.1.1.20} when the reaction takes place in the presence of tRNAPhe deprived of its 3' adenosine or pCpCpA terminus . This shows that, upon interaction with tRNA, a structural alteration of the enzyme's active site is achieved . This process may be a determining step in the specificity of the aminoacylation reaction.

J Bacteriol, 1981 Mar, 145(3), 1342 - 50
Timing of ribosome synthesis during ascosporogenesis of yeast cells: evidence for early function of haploid daughter genomes; Emanuel JR et al.; During meiosis and sporulation in Saccharomyces cerevisiae, the recessive genetic marker for cycloheximide resistance, believed to be due to an altered ribosomal protein (C . S . McLaughlin, p . 815-827, in M . Nomura et al., ed., Ribosomes, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.), is expressed as early as meiosis II . Ribosomal ribonucleic acid synthesis peaks near the time that cycloheximide resistance begins to appear . Less than 25% of the 17S and 25S ribonucleic acid of the vegetative cells persists in spores, but pulse-labeling studies indicate that greater than 90% of the stable ribonucleic acid made after 6 h survives in spores . These results indicate that the haploid daughter genomes begin to function near the time of meiosis II.

Int J Radiat Biol Relat Stud Phys Chem Med, 1981 Mar, 39(3), 281 - 90
Responses of yeast cells to heat applied alone or combined with gamma-rays; Petin VG et al.; Experiments were carried out to determine the effects of hyperthermia alone or combined with gamma-rays on the survival of yeast cells of different species . Arrhenius plots for the heat inactivation of yeast cells show inflection points . This suggests that hyperthermic killing above or below these temperatures is mediated by different mechanisms . The synergism between hyperthermia and ionizing radiation was almost linearly dependent on temperature as shown by Arrhenius plots for the combined action of both modalities . The data obtained may imply that different processes are involved in heat inactivation and thermal enhancement of yeast cell radiosensitivity.

Mol Cell Biol, 1981 Mar, 1(3), 269 - 80
Ribonuclease "XlaI," an activity from Xenopus laevis oocytes that excises intervening sequences from yeast transfer ribonucleic acid precursors; Otsuka A et al.; A ribonuclease (RNase) activity, RNase "XlaI," responsible for the excision of intervening sequences from two yeast transfer ribonucleic acid (tRNA) precursors, pre-tRNA(Tyr) and pre-tRNA(3Leu), has been purified 54-fold from nuclear extracts of Xenopus laevis oocytes . The RNase preparation is essentially free of contaminating RNase . A quantitative assay for RNase XlaI was developed, and the reaction products were characterized . RNase XlaI cleavage sites in the yeast tRNA precursors were identical to those made by yeast extracts (including 3'-phosphate and 5'-hydroxyl termini) . Cleavage of pre-tRNA(3Leu) by RNase XlaI and subsequent ligation of the half-tRNA molecules do not require removal of the 5' leader or 3' trailer sequences.

Nucleic Acids Res, 1981 Feb 25, 9(4), 1031 - 44
Conformational states of yeast tRNA Phe in the complex with cognate and non cognate synthetases; Rigler R et al.; The influence of phenylalanyl-tRNA synthetase and seryl-tRNA synthetase on the conformation and structural kinetics of yeast tRNA Phe was investigated . Ethidium substituted for dihydrouracil at position 16 or 17 was used as a structural probe, showing the existence of three conformational states in tRNA . The distribution of states (T1, T2, T3) is changed only by the cognate synthetase towards T3 which probably is related to the X-ray structure . The binding of phenylalanyl-tRNA synthetase leads to an about 10-fold increase in the fast transition T1 in equilibrium or formed from T2 which has been assigned to changes in the anticodon loop conformation and to a 2-3 fold increase in the slow transition which probably extends to other parts of the tRNA molecule . The observed rates for the transition T2 in equilibrium or formed from T3 are close to that observed for the transfer of the activated phenylalanine to tRNA Phe . This raises the possibility that the conformational transition in tRNA is the rate limiting step in the charging reaction.

Nucleic Acids Res, 1981 Feb 25, 9(4), 921 - 34
Characterization of the yeast tRNA Ser genomic organization and DNA sequence; Page GS et al.; Purified, isolated yeast tRNA Ser2 was used as a hybridization probe to estimate the number of tRNA Ser2 genes in the yeast genome . Molecular clones of several of the genes were obtained . Three examples were studied in detail with respect to their genomic organization, and DNA sequences were determined for them . There appear to be eleven tRNA Ser2 genes in the yeast genome . They are neither tandemly repeated, nor clustered with other tRNA genes . They contain no intervening sequences.

Nucleic Acids Res, 1981 Feb 25, 9(4), 789 - 99
The structure of the yeast ribosomal RNA genes . 3 . Precise mapping of the 18 S and 25 S rRNA genes and structure of the adjacent regions; Bayev A et al.; The 5'-terminal of Saccharomyces cerevisiae 18 S and 25 S rRNA are precisely mapped within the sequence of the rDNA repeating unit . The 3'-terminal of 25 S rRNA and 37 S pre-rRNA are located within a 548 bp segment of the rDNA repeating unit by the use of a DNA polymerase I extension technique . The analysis of the rDNA sequences at the structural gene boundaries reveals the presence of oligonucleotide repeats which may be involved in transcription or processing control mechanisms . The sequence of rDNA in the transcription termination region is determined and possible mechanisms shaping the 3'-end of 25 S rRNA are discussed.

Nucleic Acids Res, 1981 Feb 25, 9(4), 1019 - 29
tRNA synthesis: identification of in vivo precursor tRNAs from parental and mutant yeast strains; Hopper AK et al.; In vivo yeast precursor tRNAs have been identified using a modification of the Northern-hybridization procedure . Two species of pre-tRNA Tyr, 1 species of pre-tRNA Ser2 and 2 species of pre-tRNA Serminor have been found in all yeast strains examined, including parental strains and strains harboring mutations affecting tRNA function . One of the tRNA Tyr strains harboring and one of the pre-tRNA SerUCG are the same size as the unspliced pre-tRNAs which accumulate in the yeast mutant rna1 . The in vivo tRNA Tyr precursors detected in these studies also appear similar with the RNA species identified when cloned yeast tRNA Tyr is transcribed and processed by Xenopus oocytes and/or Xenopus extracts . We have also studied the precursor and mature tRNA Tyr species from 22 mutants which contain mutations in the SUP4 tyrosine-inserting suppressor locus . The RNA from 2 mutants mapping at the G52 position showing an aberrantly migrating "mature" tRNA Tyr . Although several of those cloned mutant genes showed transcript products of altered size in in vitro transcription studies (1), we did not detect such altered transcripts in vivo.

J Biol Chem, 1981 Feb 25, 256(4), 1782 - 5
Inactivation of hydroxymethylglutaryl-CoA reductase from yeast by coenzyme A disulfide; Gilbert HF et al.; The time-dependent inactivation of hydroxymethylglutaryl-CoA reductase from yeast by solutions of hydroxymethylglutaryl-CoA and CoASH is due to the rapid inactivation of the enzyme by oxidized CoA (CoA disulfide) present at trace levels in solutions of hydroxymethylglutaryl-CoA and CoASH . Solutions of hydroxymethylglutaryl-CoA or CoASH incubated for 1.5 h with 10 mM dithiothreitol at pH 7.0, 22 degrees C, do not inactivate the enzyme . Inactivation of hydroxymethylglutaryl-CoA reductase is rapid and complete at concentrations of CoA disulfide comparable to those measured in solutions of hydroxymethylglutaryl-CoA and CoASH . Inactivation of the enzyme by CoA disulfide may be reversed by treating the inactive enzyme with 10 mM dithiothreitol at pH 7.0 Both the inactivation of the enzyme by CoA disulfide and reactivation by dithiothreitol are inhibited by hydroxymethylglutaryl-CoA . Other disulfides such as Ellman's reagent and glutathione disulfide also inactivate the enzyme . A thio-disulfide exchange reaction with a sulfhydryl group on the enzyme forming a mixed disulfide or an intramolecular protein disulfide could account for the enzyme inactivation . The normal function of the sulfhydryl group involved in the inactivation of the enzyme is unknown.

Biochim Biophys Acta, 1981 Feb 18, 673(1), 10 - 3
Alpha-glucosidase synthesis in yeast cells depleted of intramitochondrial ATP; Leskova Z et al.; We have studied the dependence on mitochondrial ATP of expression of MAL genes specifying maltose utilization in yeast . It was found that bongkrekic acid does not prevent the maltose induced synthesis of alpha-glucosidase in derepressed cells of the wild-type and corresponding respiratory-deficient mutant of Saacharomyces cerevisiae . The results suggest that expression of nuclear genes specifying alpha-glucosidase and maltose catabolism in yeast is apparently not dependent on the proper function of mitochondrial adenine nucleotide translocase and does not even require the presence of normal levels of ATP in mitochondria.

J Biol Chem, 1981 Feb 10, 256(3), 1377 - 84
The amino acid sequence of yeast enolase; Chin CC et al.; Automatic sequencing of yeast enolase and of its chemically and enzymatically produced peptide fragments has established the sequence of 416 of the 436 residues in the enolase subunits . The missing segments have been provided from results from sequencing the DNA of the yeast enolase genes (Holland, M . J., Holland, J . P., Thill, G . P., and Jackson, K . A . (1981) J . Biol . Chem . 256, 1385-1395) . The reported enolase sequence thus represents the results of two completely independent studies, which yielded identical results for 404 of the 436 residues, and which on re-examination are consistent with the reported sequence in all but nine positions . The availability of the entire yeast enolase sequence has permitted a reassessment of structure-function parameters available for the enzyme, and some implications of the sequence information on the secondary, tertiary, and quarternary structure and on the active site components of yeast enolase have been summarized and discussed.

J Biol Chem, 1981 Feb 10, 256(3), 1385 - 95
The primary structures of two yeast enolase genes . Homology between the 5' noncoding flanking regions of yeast enolase and glyceraldehyde-3-phosphate dehydrogenase genes; Holland MJ et al.; Segments of yeast genomic DNA containing two enolase structural genes have been isolated by subculture cloning procedures using a cDNA hybridization probe synthesized from purified yeast enolase mRNA . Based on restriction endonuclease and transcriptional maps of these two segments of yeast DNA, each hybrid plasmid contains a region of extensive nucleotide sequence homology which forms hybrids with the cDNA probe . The DNA sequences which flank this homologous region in the two hybrid plasmids are nonhomologous indicating that these sequences are nontandemly repeated in the yeast genome . The complete nucleotide sequence of the coding as well as the flanking noncoding regions of these genes has been determined . The amino acid sequence predicted from one reading frame of both structural genes is extremely similar to that determined for yeast enolase (Chin, C . C . Q., Brewer, J . M., Eckard, E., and Wold, F . (1981) J . Biol . Chem . 256, 1370-1376), confirming that these isolated structural genes encode yeast enolase . The nucleotide sequences of the coding regions of the genes are approximately 95% homologous, and neither gene contains an intervening sequence . Codon utilization in the enolase genes follows the same biased pattern previously described for two yeast glyceraldehyde-3-phosphate dehydrogenase structural genes (Holland, J . P., and Holland, M . J . (1980) J . Biol . Chem . 255, 2596-2605) . DNA blotting analysis confirmed that the isolated segments of yeast DNA are colinear with yeast genomic DNA and that there are two nontandemly repeated enolase genes per haploid yeast genome . The noncoding portions of the two enolase genes adjacent to the initiation and termination codons are approximately 70% homologous and contain sequences thought to be involved in the synthesis and processing messenger RNA . Finally there are regions of extensive homology between the two enolase structural genes and two yeast glyceraldehyde-3-phosphate dehydrogenase structural genes within the 5- noncoding portions of these glycolytic genes.

Biochim Biophys Acta, 1981 Feb 5, 672(3), 313 - 6
The effect of spermine on the interaction of AMP deaminase with threonine dehydratase activity in yeast; Yoshino M et al.; Evidence suggesting that AMP deaminase (EC 3.5.4.6) is responsible for the stimulation of threonine dehydratase (EC 4.2.1.16) activity in situ is presented using yeast cells which have been rendered permeable . The addition of polyamine, an activator of AMP deaminase, resulted in the increase in ammonia concentration, which can stimulate the activity of yeast threonine dehydratase . Polyamine may regulate the synthesis of isoleucine and valine, and of the intermediates of citric acid cycle through the activation of AMP deaminase-threonine dehydratase system as a 'cascade system' in yeast.

J Clin Microbiol, 1981 Feb, 13(2), 393 - 4
Rapid detection of yeast enzymes by using 4-methylumbelliferyl substrates; Bobey DG et al.; In a preliminary study with a limited number of isolates, the usefulness of 17 4-methylumbelliferyl substrates for identifying yeast isolates was investigated . Substrates to detect acid phosphatase, glucosidase, and pyrophosphate diesterase showed promise.

J Inorg Biochem, 1981 Feb, 14(1), 33 - 44
Binding of terbium (III) to yeast enolase; Brewer JM et al.; Several independent criteria indicate 2 mol of terbium (III) bind to yeast enolase in the absence of substrate-fluorescence titrations of enzyme and metal, effects on thermal stability and published ultrafiltration and inhibition experiments . These measurements also suggest the terbium binding sites are the same as those normally occupied by "conformational" magnesium . Terbium binds much more strongly than magnesium, however, and measurements of the kinetics of the absorbance change in the terbium-enzyme on adding excess EDTA suggest the terbium-enzyme dissociation constant is about 1/500 that of the magnesium-enzyme . Measurements of enzyme activity as a function of substrate concentration show that terbium permits no enzymatic activity . However, magnesium competes more effectively with the lanthanide if the substrate analogue 3-aminoenolpyruvate 2-phosphate (AEP) is present . The fluorescence of the lanthanide is not readily observed on exciting the terbium-enzyme at 280 nm, indicating the absence of tyrosines or tryptophans in the coordination sphere of the metal . Excitation of terbium using 488 nm radiation from an argon ion laser shows the fluorescence of the metal is enhanced by binding to the enzyme . EDTA and carbonate have similar effects . This suggests carboxyl groups are involved in binding metal at the conformational sites of yeast enolase . Measurements of lifetimes of enzyme-bound terbium in the presence and absence of D2O indicated three moles of water remained on each of the bound metals, independently of the buffer used . If enzyme-bound terbium is assumed to be nine-coordinate, the metal must bind to six groups from the enzyme . The presence of substrate does not markedly affect the emission spectrum of the bound terbium or the number of water molecules remaining on the metal, but calorimetric measurements show that substrate binds to the terbium enzyme.

Arch Microbiol, 1981 Feb, 128(4), 394 - 7
Accumulation of pyrophosphate and other energy-rich phosphorous compounds under various conditions of yeast growth; Ermakova SA et al.; In the cells of hybrid yeast strain Saccharomyces N.C.Y.C . 644 SU3 (Karlsberg collection), a large amount of pyrophosphate (30-300 micro mol per g of dry weight) accumulates whatever the aeration conditions and the contest of glucose in the medium . The content of pyrophosphate is 10-100 times higher than that of ATP . At the early and mid-exponential growth phases two maxima of pyrophosphate accumulation are observable . The periods of maximal pyrophosphate accumulation in yeast coincide with those of the minimal contest of polymeric acid-soluble polyphosphates and intense budding . In the light of the data obtained, the question is discussed as to the relationship between the metabolism of pyrophosphates and acid-soluble polyphosphates in yeats.

Cell, 1981 Feb, 23(2), 605 - 14
Transposable elements associated with constitutive expression of yeast alcohol dehydrogenase II; Williamson VM et al.; The yeast structural gene ADR2, coding for the glucose-repressible alcohol dehydrogenase (ADHII), has been isolated by complementation of function in transformed yeast . The chromosomal DNA from nine yeast strains with cis-dominant constitutive mutations (ADR3c) has been investigated by restriction enzyme analysis, using the cloned ADR2 DNA as a hybridization probe . Seven mutants appear to have insertions of approximately 5.6 kg near the 5' end of the ADR2-coding region . Four of these insertions have the same restriction pattern as the yeast transposable element Ty1 . Two differ from Ty1 by the presence of an additional Hind III site, and a seventh insertion differs from Ty1 at a number of restriction sites . All are inserted in the same orientation with respect to the structural gene . A DNA fragment containing the ADR2 gene and adjacent sequences from a constitutive mutant has been cloned and shown by heteroduplex analysis to contain an insertion near the 5' end of the structural gene . The cloned insertion sequence hybridizes to multiple genomic DNA fragments, indicating that it contains a moderately repetitive sequence . Thus it appears that insertion of a transposable element near the 5' terminus of the structural gene can produce constitutive expression of a normally glucose-repressed enzyme . Such insertions seem to be the most common way of generating cis-dominant constitutive mutations of ADHII.

Biochim Biophys Acta, 1981 Jan 29, 652(1), 129 - 38
The occurrence of two ribosomal ribonucleases depending on growth phase in yeast . Induction of ribonuclease in glucose-starved cells; Swida U et al.; There are two latent ribonucleases associated with the 40 S subunits of yeast ribosomes which differ in their digestion products, pH optimum, molecular weight, and in their activity during growth phase . The 3'-nucleotide-producing enzyme is active only in the late logarithmic or stationary growth phase, whereas the ribonuclease which produces 5'-nucleotides is present at all growth phases . The enzymes were separated by affinity chromatography and were partially characterized . By changing growth conditions--i.e . decreasing and increasing the glucose concentration in the medium--the activity of the 3'-ribonuclease could be induced or reduced.

Biochim Biophys Acta, 1981 Jan 29, 652(1), 234 - 9
Mitochondrially synthesized protein subunits of the yeast mitochondrial adenosine triphosphatase . A reassessment; Orian JM et al.; Evidence is presented that a mitochondrial translation product (Mr, 32,000) previously thought to be a subunit of the membrane sector of the yeast mitochondrial ATPase is a contaminant, consisting of subunit II of the cytochrome oxidase complex and cytochrome b apoprotein . Our data suggest that only two subunits (Mr, 7600 and 20,000) of the mitochondrial ATPase are synthesized in the mitochondria.

Biochim Biophys Acta, 1981 Jan 29, 652(1), 82 - 9
Joining of yeast alanine transfer ribonucleic acid half molecules to form a whole molecule by T4 RNA ligase; Wang GH et al.; Covalent joining of the two half molecules of tRNAAla by T4 RNA ligase to form a reconstituted whole molecule was investigated . The two half molecules consisting, respectively, of residues 1-35 and 36-75 were prepared by partial degradation of tRNAAla with RNAase T1 . The 5'-half molecule was treated with alkaline phosphatase to remove the 3'-terminal phosphate group, and the 5'-OH group of the 3'-half molecule was phosphorylated with {gamma-32P}ATP by polynucleotide kinase . The two terminal nucletides to be joined were identified as Guo and Cyd . Prior to the covalent joining reaction, the two modified half molecules in an equimolar mixture were annealed, and the rejoined half molecules, separated by gel electrophoresis, served as the substrate for T4 RNA ligase . Optimum conditions for this ligation, such as RNA ligase concentration, pH, Mg2+ concentration, reaction temperature and time of reaction, were investigated . Under the optimum conditions a yield of about 70% joining of the reconstituted whole molecule was obtained as shown by gel electrophoresis, resistance to hydrolysis by alkaline phosphatase, nearest neighbour analysis and alanine acdeptor activity.

Biochim Biophys Acta, 1981 Jan 26, 663(1), 194 - 202
Involvement of cytochrome b5 and a cyanide-sensitive monooxygenase in the 4-demethylation of 4,4-dimethylzymosterol by yeast microsomes; Aoyama Y et al.; According to Ohba et al . (Ohba, M., Sato, R., Yoshida, Y., Nishino, T . and Katsuki, H . (1978) Biochem . Biophys . Res . Commun . 85, 21-27), yeast microsomes catalyze the removal of three methyl groups attached to the C-4 and C-14 positions of {1,7,15,22,26,30-14C}lanosterol (4,4,14 alpha-trimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol) in the presence of NADPH, NAD+ and molecular oxygen, concomitant with the liberation of 14CO2 derived from C-30 (one of the two methyl groups at the C-4 position) . In this process the methyl group at the C-14 position is first removed in a cyanide-insensitive reaction and then the two methyl groups at the C-4 position are removed by a cyanide-sensitive enzyme system . In this study it was found that the 14CO2 formation from the 14C-labeled lanosterol was inhibited by antibodies to yeast cytochrome b5 and by palmitoyl-CoA, a substrate of the cytochrome b5-containing fatty acyl-CoA desaturase system of yeast microsomes . However, neither the antibodies nor palmitoyl-CoA inhibited the conversion of lanosterol to 4,4-dimethyl zymosterol (4,4-dimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol) . It is concluded that cytochrome b5 and a cyanide-sensitive enzyme are involved in the 4-demethylation of 4,4-dimethylzymosterol, but not the 14 alpha-demethylation of lanosterol, by yeast microsomes . It is suggested that a cyanide-sensitive enzyme acts as the terminal 4-demethylase and cytochrome b5 transfers reducing equivalents from NADPH to the terminal enzyme, as in the case of fatty acyl-CoA desaturation . The cyanide sensitivity of the 4-demethylation was, however, much greater than that of the desaturation.

J Biol Chem, 1981 Jan 25, 256(2), 557 - 9
Binding of citreoviridin to the beta subunit of the yeast F1-ATPase; Gause EM et al.; Citreoviridin, a nonfluorescent inhibitor of bovine and bacterial ATPases, also inhibits the yeast F1 (K1 = 2 microM) . The beta subunit-specific fluorescent ligand, aurovertin, has been used to report the interaction of citreoviridin with the yeast F1-ATPase and the isolated beta subunit . Citreoviridin caused a marked decrease in the fluorescence increment associated with the binding of aurovertin to either intact F1 or the isolated beta subunit . Three lines of evidence indicate that citreoviridin and aurovertin bind to nonidentical sites on the beta subunit: 1) the binding of citreoviridin to the F1 or isolated beta subunit is noncompetitive with respect to aurovertin; 2) the number of aurovertin binding sites (Kd = 0.2 to 0.6 microM) per F1-ATPase molecule remains the same (1.89 +/- 0.6 mol of aurovertin bound per mol of F1) in the presence or absence of citreoviridin; 3) the F1-ATPase obtained from the aurovertin-resistant mutant aur-1 is partly inhibited by citreoviridin.

Nature, 1981 Jan 22, 289(5795), 250 - 2
Homology and non-homology at the yeast mating type locus; Sprague GF Jr et al.; Four mutations of the alpha mating type locus of Saccharomyces cerevisiae have been analysed to determine their relationship to the a mating type locus . Mat alpha+ recombinations are produced by mat alpha 2-/MAT but not by mat alpha 1-/MATa diploids . MAT alpha and MATa thus contain regions of homology (coding for at least part of MAT alpha 2) and regions of non-homology (coding for at least part of MAT alpha 1)-the genetic determinant for cell type is larger than the non-homologous sequence seen by DNA-DNA heteroduplexes and genetic analysis . The segment transposed in mating type interconversion includes both types of sequence.

Nature, 1981 Jan 22, 289(5795), 244 - 50
A position effect in the control of transcription at yeast mating type loci; Nasmyth KA et al.; The two mating type loci MATa and MAT alpha each produce two mRNAs that are transcribed in opposite and diverging directions from central promoters . Silent copies of MATa (HMRa) and MAT alpha (HML alpha) contain identical DNA sequences throughout the transcribed region, yet are not transcribed . It is concluded that sequences to the left of HMRa (and probably HML alpha) must somehow affect transcription initiated at the centre of each locus 700 to 1,400 base pairs away . A possible mechanism for this position effect is discussed.

Nature, 1981 Jan 22, 289(5795), 239 - 44
Regulation of transcription in expressed and unexpressed mating type cassettes of yeast; Klar AJ et al.; The genes that control the a, alpha and a/alpha cell types in Saccharomyces are carried on transposable elements known as a and alpha cassettes which reside at three different chromosomal loci . Examination of the transcripts by R-looping and filter hybridization indicates that each cassette is capable of producing two divergent transcripts . Cassettes at the MAT locus are transcribed constitutively . Transcription of cassettes at HML and HMR is prevented by trans-acting negative regulators.

Biochem J, 1981 Jan 15, 194(1), 63 - 70
The role of glutathione in amino-acid absorption . Lack of correlation between glutathione turnover and amino-acid absorption by the yeast Candida utilis; Robins RJ et al.; The rate of degradation of glutathione has been determined in the yeast Candida utilis by using a method that minimizes the effect of amino-acid recycling . When yeast are grown in amino-acid-free medium, the half-life of glutathione was found to be 230 min . C . utilis was also found to absorb various L-amino acids rapidly without producing any significant decrease in the half-life of glutathione . While the gamma-glutamyl cycle is thus operating in C . utilis, the rate of degradation of glutathione is found to be 100 times too slow for the cycle to be mediating the transport of these amino acids.

Nature, 1981 Jan 15, 289(5794), 144 - 8
Intrachromosomal gene conversion in yeast; Klein HL et al.; We have shown that the yeast Saccharomyces cerevisiae has a mechanism by which information from one gene can be transferred non-reciprocally to a repeated copy of the gene on the same chromosome . This intrachromosomal gene conversion may be important in maintaining sequence homogeneity within families of repeated eukaryotic genes.

Nucleic Acids Res, 1981 Jan 10, 9(1), 31 - 45
Efficient and selective initiation by yeast RNA polymerase B in a dinucleotide-primed reaction; Lescure B et al.; Yeast RNA polymerase B catalyzes an efficient abortive initiation on double-stranded DNA templates using the appropriate combination of primer and substrate . The specificity of initiation was investigated using a recombinant plasmid (pJD14 DNA) containing the structural gene for yeast alcohol dehydrogenase I (ADHI) . The combination of the dinucleotide UpA and UTP was 10 fold more efficient with pJD14 DNA than with the vector pBR322 DNA to direct the synthesis of the trinucleotide UpApU . Under these conditions, stable enzyme-DNA complexes were formed and could be retained on nitrocellulose filters . Using the UpA-primed system and a short pulse of RNA synthesis, transcription complexes were located on the yeast part of pJD14 DNA as evidenced by agarose gel electrophoresis . Southern hybridization of the pulsed RNA was restricted to a region, within the yeast DNA fragment, upstream to the initial region of the ADHI gene.

Biochim Biophys Acta, 1981 Jan 8, 640(1), 352 - 8
Energy source for lithium efflux in yeast; Rodriguez-Navarro A et al.; The efflux of Li+ in yeast was found to depend on the protonmotive force . The ATP content of the cell regulated the efflux that was also sensitive to the decrease in the cell pH . We propose an electrogenic H+/Li+ antiport as the mechanism for the efflux of Li+.

J Cancer Res Clin Oncol, 1981, 102(2), 127 - 39
Polycyclic aromatic hydrocarbons and possible metabolites: convertogenic activity in yeast and tumor initiating activity in mouse skin; Siebert D et al.; The diploid respiratory-deficient strain of yeast D4-RDII was used to assay PAH and urethane as well as some oxygenated derivatives of PAH and the (aliphatic) epoxide hydrolase inhibitor TCPO for convertogenic (mutagenic) activity . As a positive control, the convertogenic ultimate rat liver carcinogen NOAcAAF was used . PAH and urethane were found inactive as convertogens, TCPO was weakly active, whereas oxygenated electrophilic derivatives of PAH, such as K-region oxides, were found strong convertogens . For comparison, some convertogenic key compounds were assayed for their tumor-initiating activity in mouse skin in the standardized system using TPA as a promotor . PAH were stronger initiators than all oxygenated derivatives of PAH tested . TCPO alone exhibited very weak, if any, initiating activity . It was unable to modify initiation to any significant extent, if administered 5 min prior to administration of an initiator . In the absence of correlation between convertogenic and initiating activity the question of the chemical nature of "ultimate initiators" of mouse skin carcinogenesis awaits further investigation.

Z Allg Mikrobiol, 1981, 21(9), 643 - 50
{Structure of the cell wall polysaccharide in the food protein yeast Candida spec . H . VI . Isolation and structure of the glucans}; Grimmecke HD et al.; Alkali-soluble glucan was obtained from Candida spec . H by extraction with dilute sodium hydroxide . This minor component is quite heterogeneous in molecular size, has a highly branched structure and contains 19% beta (1,3)-, 24% beta (1,6)- and only 2% beta (1,2)-linkages . Other minor polysaccharide components have been isolated by acetic acid extraction . They have been identified as glycogen and linear beta(1,6)-glucan, respectively . The major component is a 1,2-, 1,3,-, 1,6-glucan branched in 1,2,3-, 1,3,6- and 1,2,6-positions, containing chitin . So we can confirm that different yeasts may differ in glucan structures which vary considerably both in the degree of branching and molecular size.

Int J Neurosci, 1981, 13(4), 219 - 27
Ontogenetic alterations of the cerebral cortex in rat caused by a diet containing a lipid fraction extracted from yeast (Candida lipolytica) grown on N-alkanes; Gozzo S et al.; Several ontogenetic aspects of the cerebral cortex were studied in rats whose mothers were fed on a diet, the lipid fraction of which was extracted from yeast (Candida lipolytica) grown on N-alkanes, during part of pregnancy and throughout lactation . Measures of the heights of some cortical regions and specific layers, the maturation of mean cell volumes and of the cell/gray coefficient, especially in layers I, IV and VI, show that the diet affects cerebral cortex ontogeny . These effects on brain ontogeny and on intrinsic and extrinsic neuron connections may explain the electrophysiological and behavioural alterations observed in previous studies.

Z Allg Mikrobiol, 1981, 21(3), 211 - 8
{Structure of the cell wall polysaccharide in the food protein yeast Candida spec . H . IV . Structure of the alkali labile oligosaccharide in the mannan-protein-phosphate complex}; Grimmecke HD et al.; Mild alkaline degradation of the proteophosphomannan (PPM) under conditions that effect beta-elimination of the residues, O-glycosidically bound on serine and threonine, release mainly mannose, glucose, mannobioses and mannotrioses with the same structures as those obtained by acetolysis of the polysaccharide component of the PPM . Methylation analysis and paper chromatography demonstrated the structural heterogeneity of the tetra-, penta- and hexasaccharide fractions containing 1,2- and 1,6-linked and 1,2,6-branched manno-oligosaccharides . Methylation analysis and acetolysis, paper chromatography and analysis of the carbohydrate composition of the oligosaccharide fractions DP 7-12 and DP 15-19 demonstrated inner core region like structures containing 1,2- and 1,6-linked mannose, 1,2,6- and 1,3,6-branchpoints and N-acetyl-D-glucosamine.

Z Allg Mikrobiol, 1981, 21(3), 201 - 10
{Structure of the cell wall polysaccharide in the food protein yeast Candida spec H . III . Characterization of different phosphate bonds in the mannan-protein-phosphate complex}; Grimmecke HD et al.; The 31P-NMR spectra of the proteophosphomannan (PPM) and also that of mildly hydrolyzed PPM demonstrated phosphomonoester (in both preparations), acid labile and acid stable phosphodiester linkage, and polyphosphate . Decreasing in size by pronase digestion, separation, purification and characterization of the high and low molecular phosphates by 31P-NMR spectroscopy and chemical analysis revealed the mannan protein is phosphorylated in the N-glycosidically linked carbohydrate parts and in the O-glycosidically linked oligosaccharides . Another phosphate serves as a bridge between the serine of the protein and mannose, mannobioses and mannotrioses and between the threonine and a lipophilic acylglycerid unit . The origin of the polyphosphates has been discussed.

Z Allg Mikrobiol, 1981, 21(2), 95 - 107
{Cell wall polysaccharide structure in the food protein yeast, Candida spec . H . I . Structure of alkali-stable mannoproteins}; Grimmecke HD et al.; The isolated manno-protein contains about 80% mannose and 10% glucose . Methylation analysis established the highly branched nature of this polysaccharide and the presence of 1,2-, 1,3- and 1,6-linkages, as well as the linkages of the branch points . The research of the acetolysis fragments revealed that the molecule is composed on mannose and mannooligosaccharides with DP2 to DP12 . These oligosaccharides are terminated in the nonreducing end by alpha(1,3)-mannose . Glucose was only found in the monosaccharide fraction corresponding to the nonsubstituted backbone and in the alpha(1,3)-disaccharide fraction (reducing and nonreducing end) of the acetolysis . A heptasaccharide fraction corresponding to the N-glycosidical linkage region between polysaccharide and protein parts of the glycoprotein had been isolated . 1H-NMR spectroscopy and chemical characterization made it probable that the unit with the first side chain, mannopentaose, is linked by di-N,N' -acetylchitobiose or by 4-0-beta-D-glucosyl-N-acetyl-D-glucosamine to the asparagine residue of the protein.

Z Allg Mikrobiol, 1981, 21(2), 109 - 16
{Cell wall polysaccharide structure in the food protein yeast, Candida spec . H . II . Characterization of phosphate binding to the mannan-protein-phosphate complex and identification of phosphodiester-bound mono- oligosaccharides}; Grimmecke HD et al.; The proteophosphomannan (PPM) obtained by extraction with citrate buffer, purification by the cetavlon method and gel filtration contains a high proportion of diesterified phosphate groups between the C-6 of a side chain mannose and another glycosidically bound carbohydrate . Mild acid hydrolysis cleaved the phosphate diester linkages to yield mono- and oligosaccharide fractions . Chemical analysis and 1H-NMR studies demonstrated the heterogeneity of the oligosaccharide fractions containing alpha(1,2)-, alpha(1,3)- and alpha(1,6)-linked manno-oligosaccharides . All repeated PPM preparations contained mono-, tri- and heptasaccharides as the phosphate bound main compounds . Galactose, arabinose, fucose, and rhamnose of the monosaccharide fraction and tetra-, penta- and hexasaccharides were not found in all preparations.

Acta Microbiol Acad Sci Hung, 1981, 28(4), 339 - 45
Protoplast fusion in the yeast Candida utilis; Delgado JM et al.; Protoplasts obtained by snail enzyme treatment from two stable auxotrophic mutants of the yeast Candida utilis were induced to fuse by the use of polyethylene glycol . The hybrids formed from the auxotrophic parental strains were selected by complementation on stabilized minimal medium . Many of the hybrids were unstable and readily dissociated into their parental strains . Others, in which parental nuclei had fused, gave stable hybrid progeny . cytological and genetic evidence of these processes is presented.

Mikrobiologiia, 1981 Jan-Feb, 50(1), 110 - 3
{Yeast capsule ultrastructure}; Gulevskaia SA et al.; The ultrastructure of capsules was studied in 12 yeast species producing extracellular polysaccharides and belonging to ascomycetous, basidiomycetous and asporogenous organisms using the method of ultrathin sections . On the whole, the structure of capsules was similar in these organisms: the capsules are formed by fibrils radially coming out of the outer surface of the cell wall . Unlike those of basidiomycetous yeasts, the capsules of ascomycetous organisms are characterized by a more ordered orientation of fibrils which run strictly parallel to one another . In the capsules of basidiomycetous organisms, fibrils usually interweave, often producing a fibrillar network; in certain species, fibrils stick together forming thick threads on the periphery of the capsule . Moreover, as a rule, these yeasts possess a distinct bright zone (halo) above the outer surface of the cell wall . These results as well as data available about the chemical composition and functions of the capsule indicate that there are radical differences the latter and the cell wall which make it possible to regard the capsule as an individual organelle of the yeast cell rather than as part of the cell wall.

Enzyme, 1981, 26(1), 49 - 53
Improved modification of yeast uricase with polyethylene glycol, accompanied with nonimmunoreactivity towards anti-uricase serum and high enzymic activity; Nishimura H et al.; The highly purified uricase from Candida utilis was modified with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2), which was synthesized from monomethoxypolyethylene glycol (MW 5,000) and cyanuric chloride . Modification of approximately 36 out of the total 98 amino groups in the uricase molecule led to the complete loss of the binding ability towards antiuricase serum from rabbit with the retention of high enzymic activity (45% of native uricase) . The modified uricale cleared more slowly from the plasma of mice compared with native uricase.

J Immunopharmacol, 1981, 3(2), 171 - 92
Inhibition of yeast phagocytosis and cell spreading by glucocorticoids in cultures of resident murine peritoneal macrophages; Grasso RJ et al.; This study was initiated to determine whether the inhibition of phagocytosis and cell spreading in cortisol-treated cultures of resident murine peritoneal macrophages are glucocorticoid-directed responses . Phagocytosis of heat-killed Saccharomyces cerevisiae and cell spreading were measured in control and steroid-treated macrophage cultures over 6 days . When the cultures were exposed to testosterone, progesterone, or epicortisol, phagocytosis and cell spreading were similar to controls . In contrast, both macrophage functions were inhibited significantly in cultures treated with cortisol, methylprednisolone, dexamethasone, and triamcinolone acetonide . In addition, the rate of phagocytosis was retarded and phagocytic indices (i.e., yeast particle number/cell) were reduced in glucocorticoid-treated cultures . Dose-response studies with dexamethasone demonstrated that the ED50 for the inhibitory effect on phagocytosis was 20 nM . These results indicate that the inhibition of yeast phagocytosis and cell spreading in the steroid-treated cultures are specific glucocorticoid-directed responses.

Mol Gen Genet, 1981, 184(3), 347 - 54
The mechanism of interallelic complementation at the INO1 locus in yeast: immunological analysis of mutants; Majumder AL et al.; The ino1 locus of yeast has been demonstrated to be the structural gene for the repressible enzyme, L-myo-inositol-1-phosphate synthase (Donahue and Henry 1981 a) . We have screened a large number of allelic representatives of the ino1 locus for the presence of protein which cross reacts with antibody produced in response to purified wild type inositol-1-phosphate synthase . Approximately 50% of all ino1 representatives screened by immunoprecipitation produce a protein of 62,000 molecular weight, identical in size to the wild type enzyme subunit . These mutants (termed crm+) were tested for expression of the 62,000 MW protein under conditions which are repressing for the wild type enzyme (greater than 25 microM exogenous inositol) . The protein produced by the crm+ mutants, like the active enzyme in wild type yeast, is repressed in the presence of high levels of exogenous inositol . In addition, we have reassessed the interallelic complementation pattern observed among mutants at the ino1 locus . The entire pattern of interallelic complementation is temperature sensitive.

Mol Gen Genet, 1981, 184(1), 46 - 51
Elevated recombination and pairing structures during meiotic arrest in yeast of the nuclear division mutant cdc5; Simchen G et al.; A diploid strain of yeast, homozygous for the mutation cdc5-1, undergoes a normal meiosis at 25 degrees C . At the nonpermissive temperature of 34 degrees C, meiosis is arrested at the first meiotic division, after premeiotic DNA replication and recombination commitment have taken place . Haploidisation commitment does not occur at 34 degrees C . Electron microscopy reveals that synaptons (synaptonemal complexes) are formed and the stage of arrest is characterised by a prevalence of "modified synaptons", which consist of paired lateral elements lacking the central elements . Prolonged incubation at this stage of arrest results in unusually high recombination levels, perhaps related to the synaptonal structures observed . Temperature shift-up experiments (transfers of cell from 25 degrees C to 34 degrees C at various times during meiosis) reveal that the CDC5 function is required for both the first and the second divisions of meiosis.

Mol Gen Genet, 1981, 183(1), 152 - 7
Radioprotecting action of chemical compounds on gamma-irradiated yeast cells of various genotypes; Petin VG et al.; The radioprotective efficiency of cysteamine and cysteine has been studied on haploid and diploid, Saccharomyces cerevisiae, wild-type and various X-ray repair deficient rad mutants . The correlation between the radioprotecting action of cysteamine and cell repair capacity was demonstrated for diploid yeasts; such a correlation was not expressed for wild-type and rad mutant haploid yeast cells . It was concluded that the radioprotective action may involve cellular recovery processes, which may be mediated by a recombination-like mechanism, for which the diploid state is required . Liquid holding recovery was shown not to participate in radioprotection, judged by the absence of the influence of cysteine on the delay of the first postradiation budding as well as by the additive action of cysteine and liquid holding recovery.

Differentiation, 1981, 19(1), 68 - 70
Modulation of a cell surface glycoprotein in yeast: acid phosphatase; Schweingruber ME et al.; Upon inorganic phosphate starvation the cell wall glycoprotein acid phosphatase of yeast Saccharomyces cerevisiae is derepressed . Purified acid phosphatase isolated from early log phase cells differs in reactivity and stability from acid phosphatase from late log phase cells indicating that the two enzymes are structurally different . This demonstrates that the yeast cell has not only the capacity to regulate the amount of acid phosphatase but also the ability to vary (modulate) the structure of the secreted enzyme . Modulation of acid phosphatase may be a mechanism which is involved in morphogenetic and behavioral differentiation of the yeast cell.

Carcinogenesis, 1981, 2(11), 1201 - 5
The genetic activity of dinitropyrenes in yeast: unusual dose response curves for induced mitotic gene conversion; Wilcox P et al.; 1,6-Dinitropyrene (1,6DNP) and 1,8-dinitropyrene (1,8DNP) were tested for their ability to induce mitotic gene conversion at the trp 5 and his 4 loci in the yeast Saccharomyces cerevisiae JD1 . Both compounds were shown to be potent inducers of gene conversion in yeast, with 1,6DNP being somewhat more active than 1,8DNP . Unusual dose-response curves were obtained in that toxicity and genetic activity decreased at the higher concentrations examined . This reduction in genetic activity may reflect a decrease in the ability of yeast cells to convert the dinitropyrenes to their mutagenic forms when the concentration of the compounds exceeds a certain level.

CRC Crit Rev Biochem, 1981, 11(3), 209 - 54
Yeast enolase: mechanism of activation by metal ions; Brewer JM; Yeast enolase as prepared by current procedures is inherently chemically homogeneous, though deamidation and partial denaturation can produce electrophoretically distinct forms . A true isozyme of the enzyme exists but does not survive the purification procedure . The chemical sequence for both has been established . The enzyme behaves in solution like a compact, nearly spherical molecule of moderate hydration . Strong intramolecular forces maintain the structure of the individual subunits . The enzyme as isolated is dimeric . If dissociated in the presence of magnesium ions and substrate, then the subunits are active, but if the dissociation occurs in the absence of metal ions, they are inactive until they have reassociated and undergone a first order "annealing" process . Magnesium (II) enhances association . The interaction between the subunits is hydrophobic in character . The enzyme can bind up to 2 mol of most metal ions in "conformational" sites which then allows up to 2 mol of substrate or some substrate analogue to bind . This is not sufficient for catalysis, but conformational metal ions do more than just allow substrate binding . A change in the environment of the metal ions occurs on substrate or substrate analogue binding . There is an absolute correlation between the occurrence of a structural change undergone by the 3-amino analogue of phosphoenolpyruvate and whether the metal ions produce any level of enzymatic activity . For catalysis, two more moles of metal ions, called "catalytic", must bind . There is evidence that the enzymatic reaction involves a carbanion mechanism . It is likely that two more moles of metal ion can bind which inhibit the reaction . The requirement for 2 mol of metal ion per subunit which contribute in different ways to catalysis is exhibited by a number of other enzymes.

Neoplasma, 1981, 28(3), 281 - 9
The inhibitory effect of vinylfurans on the glycolysis in tumor and yeast cells; Drobnica L et al.; Most of the eighteen vinylfurane derivatives studied fully inhibit the glycolysis of both Ehrlich ascites carcinoma (EAC) cells and respiratory deficient yeast Saccharomyces cerevisiae at concentrations lower than 0.5 mmol/l . The inhibition of glycolysis is a consequence of some thiol enzymes inactivation . This concerns namely hexokinase (EC 2.7.1.1), glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) and especially 6-phosphofructokinase (EC 2.7.1.11) . Interference of vinylfurans with energy metabolism resulted in the depression of biosynthetic processes followed (14C-precursors incorporation into proteins and nucleic acids) and finally in the loss of EAC cell transplantability.

Mol Gen Genet, 1981, 181(4), 420 - 3
Fine structure of the 21S ribosomal RNA region on yeast mitochondrial DNA . IV . Characterization of the omega neutral allele; Bos JL; The omega locus controls the polarity of recombination and transmission of genetic markers in the 21S ribosomal RNA region in yeast mtDNA . Polarity is observed in crosses between omega+ and omega- strains . These two strains differ by the presence of an intervening sequence in the 21S ribosomal RNA gene of omega+ strains . Mutations of the omega- allele, omega neutral (omegan), can eliminate the polarity effect . We have made DNA:RNA hybrids containing ribosomal RNA from an omegan strain and mtDNA from Saccharomyces carlsbergensis (identical to omega- in the nucleotide sequence of the omega region) . These hybrids contain no mismatch at the omega region detectable by digestion with S1 nuclease . We conclude that omegan differs from omega- only in a point mutation or analogous small alteration and that the omegan mutation can result either in a Cr phenotype (omeganCr) or in the phenotypic suppression of pre-existing Cr mutations (omegenCs) . All results can be explained by a model which postulates interaction in the ribosome between the Cr and omegan regions of the ribosomal RNA and interference of the omegan mutation with splicing of the precursor ribosomal RNA in omega+ strains . The mechanism of omega-directed polarity is discussed.

Folia Microbiol (Praha), 1981, 26(2), 107 - 11
A simple procedure to obtain yeast hexokinase free of glucosephosphate isomerase and mannosephosphate isomerase; Cabrera V et al.; A hexokinase preparation was obtained from a Saccharomyces cerevisiae mutant strain deficient in glucosephosphate isomerase (GPI) and mannosephosphate isomerase (MPI) by precipitation with ammonium sulfate . The supernatant fraction corresponding to 40-60 % saturation showed the lowest content in GPI and MPI activity . The fraction was used without further purification in the determination of glucose, either free or in a mixture with fructose and mannose . The results were similar to those obtained with pure commercial hexokinase.

Folia Microbiol (Praha), 1981, 26(2), 103 - 6
Use of permeabilized yeast cells as a system of enzyme immobilization . Its use for the preparation of mannose 6-phosphate; Pascual C et al.; It was shown that hexokinase contained inside permeabilized yeast cells can be used successfully in the phosphorylation of mannose for the production of mannose 6-phosphate . We propose that enzymes entrapped within the semipermeable cell membrane be considered as an extension of the enzyme immobilization concept, since it shares many of its advantages and several of its properties with some unique characteristics.

Genetika, 1981, 17(5), 814 - 21
{Combined action of UV light and alpha particles on yeast cells of different genotypes}; Komarov VP et al.; Combined action of ultraviolet (UV) light and alpha-particles on yeast cells of different genotypes has been studied . Under combined action, after small doses of UV-light the oscillated changes of cell survival were registered for wild-type cells independent of the ploidy and the sequence of application of radiations . Additive effect of high doses of UV-light and ionizing radiation was expressed for strains incapable of the recovery of damages induced by ionizing radiation . For yeast cells possessing such a capability, the synergistic interaction of damages inflicted by high doses of UV-light and alpha-particles was noted . Possible reasons of the observed cell responses are discussed.

Clin Exp Immunol, 1981 Jan, 43(1), 208 - 14
Polymorphonuclear neutrophil iodination response as an estimate of defective yeast opsonization; Roberton DM et al.; Polymorphonuclear neutrophil iodide uptake can be used as a measure of yeast opsonization and optimal assay conditions are described for the identification of sera defective in this function . The use of standard normal and defective sera permits correction of inter-assay variations resulting from the use of different cell donors . The iodination assay correlated well (r = 0.74, P less than 0.001) with a direct assay of yeast opsonization when both were used to measure this function in a panel of 72 sera . Differences in results between the two assay systems for some sera may be explained by a requirement for two different surface-associated opsonic molecules in the initiation of neutrophil metabolic activity.

Proc Natl Acad Sci U S A, 1981 Jan, 78(1), 494 - 8
Gene conversion at the var1 locus on yeast mitochondrial DNA; Strausberg RL et al.; Alleles of the var1 locus on yeast mtDNA determine the apparent size of the mitochondrial translation product, var1 polypeptide . We have analyzed most of the different var1 alleles in our collection, which number at least 15, and have developed procedures and a genetic rationale for determining their origin and predicting their behavior in crosses . The var1 alleles are characterized by two genetically defined segments, designated a and b, which can move from one var1 allele to another by asymmetric gene conversion . We show that the a segment behaves as an entity in recombination; it is either present in or absent from different var1 alleles . The b segment usually, but not always, recombines as an entity; in some cases, only portions of the b segment recombine by gene conversion . Thus, the total number of electrophoretically resolvable var1 species we observe is explained by the assortment of a, b, and partial b segments . Each segment recombines at a characteristic frequency; however, one example is presented which shows that the recipient can modulate the frequency of gene conversion . Finally, we show that, like the 21S rDNA region (omega), there is polarity of gene conversion within var1.

Proc Natl Acad Sci U S A, 1981 Jan, 78(1), 415 - 9
Yeast tRNA precursor mutated at a splice junction is correctly processed in vivo; Colby D et al.; Yeast mutants with decreased expression of a tRNATyr gene were obtained by selection for functional inactivation of the tyrosine-inserting ochre suppressor SUP4 and subsequent screening for production of the tRNA gene product in vivo . One mutant with reduced suppressor activity was characterized by a decreased quantity of the suppressor-specific tRNA; a precursor to this tRNA, matured at both 5' and 3' termini but still containing a 14-nucleotide intervening sequence, was present in an amount greater than 7-fold that in the parent . By RNA sequence analysis of the accumulated precursor, we have identified the mutation as an A leads to G transition at the 5' splice junction . Similar analysis of the mature tRNA produced in this mutant demonstrated that the intervening sequence was accurately excised . We conclude that the specific sequence of nucleotides at this splice junction affects the efficiency but not the fidelity of processing.

Proc Natl Acad Sci U S A, 1981 Jan, 78(1), 238 - 42
Cloning of yeast gene for trichodermin resistance and ribosomal protein L3; Fried HM et al.; Yeast cells sensitive to the eukaryotic protein synthesis inhibitor trichodermin have been transformed with autonomously replicating recombinant plasmids carrying DNA fragments of the genome of a trichodermin-resistant yeast strain . After selection for trichodermin-resistant cells, several transformants yielded a plasmid containing a 13.5-kilobase (kb) DNA fragment that encodes the trichodermin resistance gene, tcm1, and the gene for ribosomal protein L3, the largest of the yeast ribosomal proteins . Cells carrying this plasmid are resistant to trichodermin and to the related drug verrucarin A as well as to the unrelated drug anisomycin . This pattern of resistance is similar to that exhibited by strains carrying a chromosomal copy of tcm1 . Moreover, polyribosomes prepared from transformed cells are resistant to trichodermin when tested in an in vitro protein synthesis assay . Subcloning of the 13.5-kb DNA fragment revealed that the gene for tcm1 and the gene for protein L3 are contained within a 3.2-kb segment . These results suggest that the gene for trichodermin resistance in yeast specifies ribosomal protein L3.

Mol Gen Genet, 1981, 181(3), 346 - 51
Isolation of yeast mutants sensitive to the bifunctional alkylating agent nitrogen mustard; Ruhland A et al.; Mutants of Saccharomyces cerevisiae with enhanced sensitivity to the DNA cross-linking agent nitrogen mustard (HN2) have been isolated and partially characterized with respect to their phenotypic and genetic properties . The screening technique, based on HN2-sensitivity as sole criterion, yields approxiamtely 1 sensitive isolate in 200 clones when applied to an intensively mutagenized population of a resistant parent strain . Mutants characterized so far are all due to recessive nuclear genes and represent at least seven complementation groups . They exhibit different degrees as well as different patterns of sensitivity towards monofunctional and bifunctional alkylating agents, and ultraviolet light.

Chromosoma, 1981, 82(3), 333 - 40
Nuclear morphology of yeast under thymidylate starvation; Moens PB et al.; During early meiotic development the yeast Saccharomyces cerevisiae has a characteristic nuclear dense body (NDB) . It is shown that the NDB can also be induced in vegetatively growing cells through the inhibition of thymidylate synthetase which causes depletion of the dTMP pool and arrests DNA synthesis . The observations on NDBs and recombination levels suggest that thymidylate-stressed cells may activate parts of the meiotic pathway and, conversely, cells on sporulation medium may sense, among other things, reduced thymidylate levels and respond to the several stimuli by entering the meiotic pathway.

Mol Gen Genet, 1981, 181(1), 147 - 9
Correspondent reaction of mitotic recombination in yeast and sister chromatid exchange in human lymphocytes; Fahrig R; In the lower eukaryote Saccharomyces cerevisiae, 4,5,6-trichloro-2-(dichlorophenoxy)phenol and acridine orange cause different specific genetic alterations, either gene mutations or recombinations . These specific effects were used to characterize the mechanism of sister chromatid exchange (SCE) formation in human lymphocytes . Assuming that genetically active substances have comparable effects in lower and higher eukaryotes, the observations provide indirect evidence for a connection between induced mitotic recombination in yeast and SCEs in human lymphocytes and suggest that SCEs may be the consequence of a repair process.

Biochimie, 1981 Jan, 63(1), 67 - 9
{Isolation of yeast protoplasts using various preparations of the hepato-pancreatic juice of Helix pomatia}; Diatewa M et al.; Conversion of large amounts of Saccharomyces cerevisiae cells to protoplasts is studied using various preparations extracted from Helix pomatia hepato-pancreatic juice . The most favourable yield in two hours incubations (88 per cent) is obtained with 20 ml cytohelicase, a chitinase and glucanase enriched extract, per 400 g of yeast cells, harvested at the end of the logarithmic growth phase and preincubated in presence of 2-mercaptoethanol.

Z Naturforsch {C}, 1981 Jan-Feb, 36(1-2), 142 - 8
Initiation of protein synthesis in yeast: binding of Met-tRNAi; Kreutzfeldt C; Conditions for the binding of Met-tRNAi to 40 s ribosomal subunits and to proteins isolated out of the yeast ribosomal KCl wash were investigated . Sucrose density gradient experiments revealed that binding of Met-tRNAi to 40 s ribosomal subunits was catalyzed in a AUG and GTP dependent reaction . Binding of Met-tRNAi to proteins of the ribosomal KCl wash as assayed by the Millipore filter technique was found to be independent of AUG, GTP and 40 s ribosomal subunits . Additions of GTP yielded only slight stimulation, whereas Mg2+ caused dissociation of complexes . It was concluded that these reactions were most likely catalyzed by initiation factor eIF-2 although stimulation by GTP did not occur.

Biokhimiia, 1981 Jan, 46(1), 140 - 7
{Cause of the activity loss of the alternative pathway of electron transport in cyanide-resistant mitochondria of the yeast Candida lipolytica}; Akimenko VK et al.; The cause of the activity loss of alternative pathway of electron transport in mitochondria of the yeast Candida lipolytica has been investigated . Incubation of cyanide-resistant mitochondria at 25 degrees was shown to cause the loss by mitochondria of their ability to oxidize substrates in the presence of 1 mM cyanide . This suggests that in the course of incubation the alternative pathway loses its activity . Repeated washing of mitochondria with a solution containing 2,5 mM EDTA inhibits, while Ca2+, Mn2+, Cu2+ and Zn2+ (but not Sr2+) enhance the process of the activity loss of the alternative pathway . The loss of the cyanide-resistant respiration is also observed during incubation of mitochondria in the presence of phospholipases A, C and D or lysolecithin . In all cases studied the reactivation of the cyanide-resistant respiration of mitochondria is attained by addition of azolectin . The loss of cyanide-resistant respiration is accompanied by the activity reduction of the main respiratory chain, which is restored by addition of cytochrome c and Mg2+ . These data indicate that the activity loss of the alternative pathway is not related to inactivation of any components in the alternative pathway itself or in the main respiratory chain . The most probable cause of the activity loss in the destruction of reducing equivalents in the alternative pathway of a donor as a result of a break of the structural entity of the internal membrane of mitochondria due to the detersive action of the phospholipid lysoforms produced either by endogenic or exogenic phospholipases.

Acta Histochem Suppl, 1981, 23, 211 - 7
Polyethylene glycol induced membrane fusion in yeast protoplasts; Svoboda A; Freeze-etching and ultrathin section techniques were used to demonstrate ultrastructural change in plasma membranes during fusion of Saccharomyces cerevisiae protoplasts . Incubation of protoplasts in 30% (w/v) polyethylene glycol fed to strong reduction in the number of particles in areas of close membrane contact and disappearance of invaginations . On sections, neighbouring plasma membranes merged to pentalaminar or trilaminar structures . After incubation in regeneration medium, these membrane changes progressed to form rounded bulging areas with crater-like openings which are thought to be channels through which coalescence of partner's cytoplasms may occur.

Acta Histochem Suppl, 1981, 23, 151 - 5
Plasma membrane particles in yeast protoplasts; Necas O et al.; Investigations of plasma membrane particles in Saccharomyces cerevisiae protoplasts are shortly reviewed . Particle arrangement into a hexagonal patterns is considered to reflect some minute changes in the biomembrane organization rather than functional differentiation . Plasma membrane invaginations are proved to be rigid structures capable of migrating in the fluid domain of the membrane . Density of the particles per unit area is related to the degree of membrane stretching which suggest that upon membrane extension new protein molecules are shifted towards the hydrophobic layer of the membrane.

Acta Biochim Pol, 1981, 28(1), 51 - 9
On the role of cyclic AMP-independent protein kinases in the modification of yeast ribosomal proteins in vivo; Kudlicki W et al.; Two proteins of yeast 40S ribosome subunit and four proteins of the 60S ribosome subunit were labelled in vivo with {32P}orthophosphate . Five of these proteins were phosphorylated by protein kinase 3, an enzyme which is cyclic AMP-independent and uses ATP and GTP as phosphoryl donors . Two proteins, belonging to the 60S ribosome subunit were phosphorylated by another, highly specific, cyclic AMP-independent protein kinase 1 B . Both in vivo and in vitro the most extensively phosphorylated protein species were acidic proteins, L44, L45 (according to the nomenclature of Kruiswijk & Planta, Molec . Biol . Rep., 1, 409-415, 1974) possibly corresponding to bacterial L7 and L12 proteins . The 40S ribosomal protein, S9, analogous to mammalian S6 protein, was phosphorylated in vivo but was not phosphorylated in vitro by either of the cyclic AMP-independent protein kinases . The obtained results clearly indicate that cyclic AMP-independent yeast protein kinases might be involved in the modification in vivo of some ribosomal proteins, in particular of the strongly acidic proteins of 60S ribosome subunit.

Nature, 1981 Jan 1, 289(5793), 33 - 7
Isolation of a gene from Drosophila by complementation in yeast; Henikoff S et al.; Transformation of mutant yeast cells by cloned genomic DNA from a higher eukaryote has made it possible to isolate a Drosophila DNA sequence that complements a yeast adenine-8-mutation . A 0.8-kilobase poly(A)-containing RNA is transcribed from the cloned Drosophila segment in transformed yeast cells and can account for functional expression of the gene.

J Histochem Cytochem, 1981 Jan, 29(1), 45 - 8
Fluorescence of yeast vitally stained with ethidium bromide and propidium iodide; Corliss DA et al.; Both ethidium bromide and propidium iodide stain growing yeast . As visualized in the fluorescence microscope, ethidium stains the nucleus and cytoplasm in wild type yeast and in those grown in 10% dextrose, with brightly fluorescent cytoplasmic granules being present in both . Under the latter conditions, the mitochondria are repressed but not absent . In rho 0 cells, in which the mitochondrial DNA is absent, ethidium appears to bind to the cell wall or membrane preferentially with no cytoplasmic granules being visible . In all cell types, propidium appears to bind the cell wall or membrane with no cytoplasmic granules being visible in any cell . The staining patterns thus suggest greater differences in the binding of these two types to mitochondrial DNA in situ than is suggested by their in vitro behavior . These differences in binding could explain their different mutagenic capacities..

Folia Microbiol (Praha), 1981, 26(1), 65 - 7
Use of ruthenium red for visualization of the regenerating cell wall in yeast protoplasts; Havelkova M; Ruthenium red was used to stain the surface of fresh and regenerating protoplasts in Saccharomyces cerevisiae . The presence of a dense layer, 10--40 nm wide, was demonstrated on the surface of most of the fresh protoplasts . This layer could be removed neither by repeated washings of protoplasts nor ;by their centrifugation . Ruthenium red proved to be a very useful dye for regenerating walls since it stained both the amorphous and the fibrillar components, but to a different degree, thus permitting their easy differentiation.

J Supramol Struct Cell Biochem, 1981, 15(2), 119 - 28
Effect of exogenous fatty acids on growth, membrane fluidity, and phospholipid fatty acid composition in yeast; Esfahani M et al.; The growth response of a double-mutant fatty acid auxotroph of yeast Saccharomyces cerevisiae to exogenous saturated fatty acids of a homologous series from 12:0 to 16:0, each supplied with oleate, linoleate, linolenate, or cis-delta 11-eicosenoate, cannot be explained in terms of the efficiency of incorporation of the fatty acids into phospholipids or alteration of membrane fluidity . There is, however, a negative correlation between growth and levels of 12:0 plus 13:0 in phospholipids, as well as a positive correlation between growth and levels of 14:0, 15:0, and 16:0 . We, therefore, conclude that the predominant factor in these phospholipid fatty acyl chain modifications is maintenance of an optimal concentration of C14:0 through C16:0 in phospholipids of this organism.

Nature, 1980 Dec 25, 288(5792), 669 - 74
Crystal structure of yeast tRNAAsp; Moras D et al.; Two independent, three-dimensional structures of yeast tRNAAsp, mainly differing by the conformation of the D loop, have been obtained from a multiple isomorphous replacement (MIR) X-ray analysis at 3.5-A resolution . The folding of the ribose-phosphate backbone is similar to that found for tRNAPhe; major differences concern the relative positioning of the acceptor and anticodon stems, and the conformation of the loops in the two molecules . Crystal packing involves self-complementary GUC anticodon interactions.

J Biol Chem, 1980 Dec 25, 255(24), 12087 - 93
Purification and properties of proteinase A from yeast; Meussdoerffer F et al.; Proteinase A (EC 3.4.23.6) was purified from commercial bakers' yeast in five steps, including hydrophobic chromatography and affinity chromatography . After the last step the enzyme appeared homogeneous on polyacrylamide gel electrophoresis and in the analytical ultracentrifuge . A molecular weight of 41,500 was determined for proteinase A . The amino acid composition includes 43% polar residues and 12% aromatic amino acids . Proteinase A is a glycoprotein containing 7.5% mannose and 1% of glucosamine and galactosamine . The temperature and the pH stability of the enzyme have been determined . At pH 6, the proteinase exhibits a remarkable stability even in 6 M urea . Proteinase A splits hemoglobin with an optimum at pH 3.0 and casein and azocasein with an optimum at pH 6.0 . The enzyme is inhibited by pepstatin, diazoacetyl-DL-norleucine methyl ester and by 1,2-epoxy-3-(4-nitro-phenoxy) propane.

J Biol Chem, 1980 Dec 25, 255(24), 11927 - 41
Assembly of the mitochondrial membrane system . Structure and nucleotide sequence of the gene coding for subunit 1 of yeast cytochrme oxidase; Bonitz SG et al.; the oxi3 locus of yeast mitochondrial DNA has been sequenced in Saccharomyces cerevisiae D273-10B . The sequence was obtained from the mitochondrial genomes of a series of cytoplasmic "petite" mutants selected for the retention of genetic markers in the oxi3 locus . The oxi3 locus has been ascertained to code for Subunit 1 of cytochrome oxidase . The Subunit 1 gene is 9,979 nucleotides long, consisting of seven to eight exons that account for only 16% of the gene sequence . The coding sequences have been identified on the basis of protein sequence homology with Subunit 1 of human cytochrome oxidase . The yeast Subunit 1 is 510 amino acid residues long and has a molecular weight of 56,000 . In addition to the exon sequences, the Subunit I gene contains six to seven introns . The first four introns have long reading frames that are continuous with the exon coding sequences . These reading frames are potentially capable of coding for basic proteins with molecular weights ranging from 30,000 to 80,000 . The first two introns of the gene have a sequence homology of 50%, while the reading frame of the fourth intron is 70% homologous with an intron of the apocytochrome b gene . At least five stable transcripts have been found by Northern blot hybridizations with single-stranded DNA probes containing either exon or intron sequences . A 1.9-kolobase transcript hybridizes only with probes from the exon regions of the gene . This RNA species has been tentatively identified as the fully processed messenger of Subunit 1 . Other transcripts are detected with intron probes . Three transcripts with sizes of 2.5, 2.4, and 0.85 kilobases appear to be stable excision products from the first, second, and fifth introns.

J Biol Chem, 1980 Dec 25, 255(24), 11922 - 6
Assembly of the mitochondrial membrane system . Physical map of the Oxi3 locus of yeast mitochondrial DNA; Bonitz SG et al.; The oxi3 locus of yeast mitochondrial DNA is currently thought to code for Subunit 1 of cytochrome oxidase (Tzagoloff, A., Macino, G., and Sebald, W . (1979) Annu . Rev . Biochem . 48, 419-441) . The respiratory competent strain of Saccharomyces cerevisiae D273-10B/A48 was used to obtain cytoplasmic "petite" clones enriched for genetic markers in the oci3 locus . The most complex clone studied (DS6) was ascertained to have a mitochondrial genome with a tandemly repeated segment of mtDNA 16.5 kilobases in length . The oxi3 locus was dissected by mutagenesis of DS6 with ethidium bromide and selection of new clones having less complex genotypes . Six derivative clones with genome sizes ranging from 2.3 to 6.1 kilobases have been extensively analyzed . Most of the restriction sites present in the segments of mtDNA retained by the clones have been mapped, thereby providing a detailed restriction map of the oxi3 gene . Based on the physical locations of the most distal oxi3 mutations, the gene spans approximately 10,000 nucleotides and occupies the region of wild type mtDNA from 44 to 58 map units.

Biochim Biophys Acta, 1980 Dec 15, 633(3), 376 - 85
Evidence for a highly specific protein kinase phosphorylating two strongly acidic proteins of yeast 60 S ribosomal subunit; Kudlicki W et al.; Two distinct, cyclic AMP-independent protein kinase (ATP : protein photransferase, EC 2.7.1.37) from yeast have been isolated and highly purified . The first of the enzymes, protein kinase 1 A, phosphorylates casein and phosvitin, and its cellular protein substrate is unknown . The second enzyme, protein kinase 1 B, phosphorylates two strongly acidic proteins, L44 and L45, of the 60 S ribosomal subunit.

C R Seances Acad Sci D, 1980 Dec 15, 291(13), 1037 - 40
{Importance of the parameters of temperature and natural light on stability of 2 types of L(+) lactate:cytochrome oxidoreductases (cytochromes b2) extracted from Hansenula anomala yeast}; Prats M; In this communication, we present the effect of two parameters, temperature and daylight-at high ionic strength-on the stability of H-flavocytochrome b2 solutions prepared using {H-flavocytochrome b2 (S) or not {H-flavocytochrome b2 (n) n-butanol during extraction . These two enzyme preparations presented the same behaviour towards these two parameters: in the dark, temperature was critical; in daylight, an opposite effect was observed for this parameter: the stability of samples was smaller at 0 degrees C . However, the evolution of life of the classical kinetic parameters (Km and Vm) of the enzymatic reaction is presented for three samples of H-flavocytochrome b2 (n) or (s) exposed to daylight at 20 +/- 0,1 degrees C.

Biochim Biophys Acta, 1980 Dec 11, 610(2), 221 - 8
Rapid purification of yeast mitochondrial DNA in high yield; Hudspeth ME et al.; A procedure is presented for the rapid isolation of mitochondrial DNA (mtDNA) in high yield from Saccharomyces cerevisiae . Yeast cells, which may be grown to late stationary phase, are broken by a combination of enzymatic and mechanical means; mtDNA is then isolated from a crude mitochondrial lysate by a single cycle of bisbenzimide-CsCl buoyant density centrifugation . mtDNA so isolated is at least 99.5% pure, and has a mean duplex molecular weight of 24.5 . 10(6) . In addition to mtDNA and bulk nuclear DNA, several other yeast nucleic acid species, identified as ribosomal DNA and a mixture of duplex RNAs, form discrete bands in these gradients.

C R Seances Acad Sci D, 1980 Dec 8, 291(12), 941 - 4
{Parameters influencing inactivation-dissociation/reactivation-association phenomena induced by variations of ionic strength of L (+)lactate: cytochrome c oxidoreductase (cytochrome b2) extract of the yeast Hansenula anomala}; Prats M; H-flavocytochrome b2, a tetramer enzyme, is inactivated, at low ionic strength and can be reactivated, increasing the ionic strength of the medium . The inactivation-reactivation process was structurally manifested by a dissociation-association phenomenon between subunits . It was clearly shown that the inactivation-dissociation process appeared independent of enzyme concentration whereas the reactivation-association phenomenon was enzyme concentration dependent . However, proteins protect H-flavocytochrome b2 from inactivation-dissociation, only when electrostatic interactions are possible between the two proteins: Horse heart cytochrome c was a good protector whereas serum albumin had no protector effect.

Biochim Biophys Acta, 1980 Dec 5, 620(3), 429 - 39
Effect of unsaturated fatty acids on sterol biosynthesis in yeast; Boll M et al.; Lipid-depleted yeast, grown anaerobically, contains only very low amounts of sterols . The hydroxymethylglutaryl-CoA reductase activity, the regulatory enzyme of sterol synthesis in yeast, is also low . Aeration of such cells in a buffer containing a carbon source induces hydroxymethylglutaryl-CoA reductase activity and increases sterol synthesis . The velocity of the increase depends on the carbon source present during the aeration period . Glucose and sugars that are easily converted to glucose were found to be most effective . A supplement of unsaturated fatty acids during anaerobic growth causes a several-fold greater velocity of the enzyme induction and of sterol biosynthesis . Linolenic acid (30 microM) accelerated sterol biosynthesis about 7-fold . Activities of galactokinase and galactose-1-phosphate uridyltransferase, which are involved in the conversion of galactose to glucose, increased several-fold in the supplemented cells within 6 h of aeration, concomitantly with stimulation of sterol synthesis from galactose . It is suggested that the stimulation of enzyme induction and sterol biosynthesis in fatty acid supplemented cells is due to a completion of the protein-synthesizing apparatus during cell growth . A markedly enhanced capacity of these cells to incorporate leucine into acid-precipitable protein supports this assumption.

Can J Microbiol, 1980 Dec, 26(12), 1428 - 37
Lipid composition and the transition from yeast-like to chlamydospore cells of Pullularia pullulans; Regulez P et al.; The lipid composition of the fungus Pullularia pullulans has been investigated at different stages of the morphogenetic transition from yeast-like, through the so-called "large cells," to chlamydospores . The first 3 days of culture correspond to the period of exponential growth . There is a rapid consumption of glucose and ammonium, until the latter becomes exhausted, and a concomitant decrease of pH down to values of about 2 . A decrease in fatty acid unsaturation takes place at this stage, together with an increase in the proportion of long-chain aldehydes . The period between days 3 and 6 is dominated by the large cells . They accumulate large amounts of triacylglycerols; phospholipids and free sterols are also synthesized in this period, suggesting de novo synthesis of membranes . Chlamydospores can be seen from the 6th day on . Simultaneously, a decrease in free sterols and phospholipids takes place, while saturated triacyglycerol production goes on . The lipid composition of chlamydospores suggests that these are resistance forms, induced by the hostile environmental conditions of the medium after the end of the exponential growth.

J Cell Sci, 1980 Dec, 46, 289 - 97
Observations on the mitochondrial reticulum in the yeast Candida utilis as revealed by freeze-fracture electron microscopy; Keyhani E; Freeze-fracture of Candida utilis yeast cells grown to early logarithmic phase (5 h) and stationary phase (24 h) revealed a branched mitochondrial reticulum both in longitudinal and transverse cross-fracture studies . In contrast, the longitudinal and transverse sections of permanganate-fixed cells showed that the small ovoid or spherical mitochondria were located at the periphery of the cell, without formation of a reticulum . Data indicate that the separate mitochondrial profiles seen in thin sections of permanganate-fixed yeast cells are not separate round or ovoid mitochondria, but rather are cross-sections of the mitochondrial reticulum.

Biochim Biophys Acta, 1980 Dec 1, 633(2), 176 - 80
Conversion of 5'-methylthioadenosine into S-adenosylmethionine by yeast cells; Shapiro SK et al.; 5'-Methylthio{U-14C}adenosine was used as a culture supplement for Candida utilis . The resulting S-adenosylmethionine was hydrolyzed into its structural components . Virtually none of the label of the pentose was found in the carbohydrate part of the intracellular S-adenosylmethionine . Much of it was present in the four-carbon chain of the methionine part of the sulfonium compound . The (U-14C)-labeled adenine of 5'-methylthio{U-14C}adenosine did not contribute to the labeling of the amino acid components of the sulfonium compound.

Cell, 1980 Dec, 22(3), 799 - 805
Histone H2B genes of yeast encode two different proteins; Wallis JW et al.; The two genetically unlinked histone H2B genes isolated from Saccharomyces cerevisiae have been sequenced . The genes encode H2B proteins that are 130 amino acids in length and that differ by 4 amino acids . The changes betwen them are Ala leads to Ser, Lys leads to Ala, Thr leads to Val and Ala leads to Val at amino acid positions 2, 3, 27 and 35, respectively . A comparison of yeast H2B histones with those of higher eucaryotes demonstrates a high degree of homology clustered mainly at the carboxyl terminus . There is extensive base substitution between the two H2B genes in nucleotides that do not affect the amino acid sequence . DNA prelude sequences show 64% divergence . The coding regions differ at 49 of the 390 bases (12.6% divergence) . 41 of these changes are in silent positions . By using the number of amino acid differences in the proteins we estimate that the two H2B genes are the result of an ancient duplication event.

J Inorg Biochem, 1980 Dec, 13(4), 353 - 66
EPR of Cu+2 binding to apo-yeast enolase; Dickinson LC et al.; We have studied the electron paramagnetic resonance (epr) spectra of complexes of apo-yeast enolase with 65Cu+2 in the presence and absence of substrate and magnesium ion . An unusual epr spectrum with large g parallel, large g and A rhombicity and very narrow line-widths (10 G) is seen for the first two 65Cu+2 bound in the presence of substrate 2-phosphoglycerate (2PGA) . the epr parameters, consistent with rhombic and tetragonal distortion of an octahedral geometry of the coordination sphere of the Cu+2 are g = (2.123, 2.042, 2.405) and A = (2.58, 4.19, 12.0) mK . The high g parallel and absence of super-hyperfine splitting are strong evidence for absence of nitrogen ligands . In the presence of Mg+2 and 2PGA, the Cu+2-enolase solutions exhibit a complex epr spectrum reflecting exchange and dipolar interaction between the first two Cu+2 ions bound . The spectra of Cu+2 plus enolase in the presence and absence of Mg+2 without 2PGA are distinct but not unambiguous, each reflecting at least two inequivalent binding sites . In addition to providing information on the geometry and location of the divalent cation binding sites, the data show unequivocally that imidazole residues, previously found to have a role in catalysis, do not participate in Cu+2 binding . Although Cu+2 does not activate the enzyme, direct binding measurements show that Cu+2 competes stoichiometrically with the activating ion, Mg+2 . A reinterpretation of earlier Mn+2 enolase studies is proposed to reconcile the Cu+2 and Mn+2 data.

Biochim Biophys Acta, 1980 Dec 1, 633(2), 211 - 27
Identification of porphyrin present in apo-cytochrome C oxidase of copper-deficient yeast cells; Keyhani E et al.; Heme a was not detected either in mitochondria isolated from copper-deficient yeast or in the intact cells . Nevertheless, the intracellular concentration of free porphyrins indicated that the pathway of porphyrin and heme synthesis was not impaired in copper-deficient cells . The immunoprecipitated apo-oxidase from copper-deficient cells revealed an absorption spectrum with maxima at 645, 592, 559, 519 and 423 nm, similar to that of purified porphyrin a . When solubilized mitochondria from {3H}leucine and delta-amino{14C}levulinic acid-labeled copper-deficient yeast cells were incubated with rabbit antiserum against cytochrome c oxidase, a precipitate was obtained . Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of this immunoprecipitate showed {3H}leucine associated with six bands and delta-amino{14C}levulinic acid resolved in a single band . HCl fractionation of copper-deficient mitochondria labeled with delta amino{14C}levulinic acid showed a high specific radioactivity in the fraction extracted by 20% HCl, a solvent which extracts porphyrin a . Thin-layer chromatography of the radioactivity found in 20% HCl showed an RF value identical to that of purified porphyrin a . When delta-amino{3H}levulinic acid-labeled, copper-deficient yeast cells are grown in copper-supplemented medium, the porphyrin a accumulated in copper-deficient cells was converted into heme a, and this conversion was prevented by cycloheximidine . These observations suggest that porphyrin a is present in the apo-oxidase of copper-deficient cells, but that the conversion to heme a does not occur . This conversion reaction appears to be a point in the biosynthetic pathway of cytochrome c oxidase which is blocked by copper deficiency.

Biochemistry, 1980 Nov 11, 19(23), 5168 - 75
Yeast 3-phosphoglycerate kinase: sulfate and substrate binding, their effect on the conformational state of the enzyme; Roustan C et al.; Anions and particularly sulfate are known to interact with 3-phosphoglycerate kinase and to induce an increase of its catalytic efficiency . The present work affords information on the location of the anionic site and on the conformational change produced by the sulfate binding . We have established that sulfate is able, first, to modify the environment of some critical amino acids (cysteine and arginines) located in the N-terminal half of the protein, second, to induce perturbation of aromatic residues as judged by spectrophotometry, and, third, to slightly decrease the magnitude of the Cotton effect at 233 nm . All these modifications are produced by sulfate concentrations required for the activation of the enzyme . The most striking result consists in a large change in the hydrodynamic properties of the protein upon sulfate interaction as determined by analytical ultracentrifugation studies . Thus, sulfate modifies the shape of the molecular, causing it to become more compact . Furthermore, a study of the binary and ternary complexes between yeast 3-phosphoglycerate kinase and its substrates suggests that such a change of the shape of the molecular only occurs in sulfate-enzyme with or without substrates and in ATP (with or without Mg2+)-3-phosphoglycerate-enzyme complexes.

Nucleic Acids Res, 1980 Nov 11, 8(21), 5007 - 16
Characterization of tRNA genes in tRNA region II of yeast mitochondrial DNA; Newman D et al.; We have isolated individual mitochondrial tRNAs from a petite mutant OI-P2-1 known to contain a limited subset of mitochondrial tRNA genes and have mapped these genes on the wild type genome of the yeast strains MH41-7B and D273-10B . To obtain DNA for fine structure mapping and DNA sequence analysis of these genes, we screened a yeast mitochondrial DNA-pBR322 recombinant bank with the isolated tRNAs . We report here the fine structure mapping of recombinant clones containing the tryptophan, formyl methionine and proline tRNA genes as well as the DNA sequence of the proline tRNA gene . The combination of restriction mapping and DNA sequence analysis has enabled us to locate these genes precisely on the wild type genome and to determine their direction of transcription.

Nucleic Acids Res, 1980 Nov 11, 8(21), 4919 - 26
The structure of the yeast ribosomal RNA genes . 2 . The nucleotide sequence of the initiation site for ribosomal RNA transcription; Bayev AA et al.; The 5'-terminal coding sequence for the 37 S precursor to rRNA of Saccharomyces cerevisiae is identified by reverse transcriptase extension and protection mapping with nuclease S1 . The sequence of a 419 bp rDNA fragment containing the transcription initiation site and its adjacent region is determined.

Nucleic Acids Res, 1980 Nov 11, 8(21), 4841 - 50
Sequence of 863 nucleotides encompassing the PstI site of the yeast 2 micron plasmid; Elleman TC et al.; The sequence of part of the larger unique region of the yeast 2 micron plasmid cloned in pMB9 has been determined . The sequence extends from the single EcoRI site in this region to the AvaI site and includes the single PstI site and HpaI site . A notable feature of this sequence is the presence of tandem repeats of 124 residues beginning at the HpaI site and extending beyond the AvaI site . The sequence was determined independently by both the Maxam-Gilbert procedure applied to isolated restriction fragments, and by the chain-termination procedure applied to restriction fragments cloned in the single-stranded phage M13mp2 and purified by plaque selection.

J Biol Chem, 1980 Nov 10, 255(21), 10188 - 93
Sulfhydryl groups of yeast phosphofructokinase-specific localization on beta subunits of fructose 6-phosphate binding sites as demonstrated by a differential chemical labeling study; Tijane MN et al.; Yeast phosphofructokinase contains 83 +/- 2 cysteinyl residues/enzyme oligomer . On the basis of their reactivity toward 5,5-dithiobis(2-nitrobenzoic acid), the accessible cysteinyl residues of the native enzyme may be classified into three groups . For titrations performed with N-ethylmaleimide, subdivisional classes of reactivity are evidenced . In each case, the 6 to 8 most reactive cysteines are not protected by fructose 6-phosphate from chemical labeling and do not seem involved in subsequent enzyme inactivation . Differential labeling studies as well as direct protection experiments in the presence of fructose 6-phosphate, indicate that 12 -SH groups/enzyme oligomer (i.e . three -SH groups per binding site) are protected by the allosteric substrate from the chemical modification . Specific labeling by the differential method of the cysteinyl residues protected by fructose 6-phosphate and further separation of the two types of subunits constituting yeast phosphofructokinase, show that the substrate binding sites are localized exclusively on subunits of beta type . Thus, alpha subunits are not implicated directly in the catalytic mechanism of yeast phosphofructokinase reaction.

Nature, 1980 Nov 6, 288(5786), 60 - 3
Leaky +1 and -1 frameshift mutations at the same site in a yeast mitochondrial gene; Fox TD et al.; Two mutations in a mitochondrial structural gene, which cause leaky premature polypeptide chain termination and leaky growth, are +1 and -1 frameshifts in the same run of five T residues . The partial restoration of reading frame is probably due to ribosomal frameshifting at this site, and may be promoted by the unique structure of the yeast mitochondrial t RNAPhe.

J Bacteriol, 1980 Nov, 144(2), 772 - 80
Significance of ribosomal ribonucleic acid synthesis for control of the G1 period in the cell cycle of the heterobasidiomycetous yeast Rhodosporidium toruloides; Yamashita I et al.; A cell cycle mutant strain which is defective in the G1 period, B2-39, was selected from 1,200 temperature-sensitive mutants of the heterobasidiomycetous yeast Rhodosporidium toruloides M-1057 . In the mutant cells, ribosomal ribonucleic acid synthesis was initially inhibited upon temperature shift-up from a permissive (25 degrees C) to a restrictive (36 degrees C) temperature . Moreover, the mutant was found to be temperature sensitive in deoxyribonucleic acid-dependent ribonucleic acid polymerase I activity in vitro . In a revertant-mutant strain, B2-39-R-2, both ribosomal ribonucleic acid synthesis in vivo and enzyme activity in vitro were simultaneously recovered . These results indicate that the mutant has a temperature-sensitive, deoxyribonucleic acid-dependent ribonucleic acid polymerase I and suggest that ribosomal ribonucleic acid synthesis acts as one of the control factors for initiation of both deoxyribonucleic acid synthesis and bud emergence.

J Bacteriol, 1980 Nov, 144(2), 721 - 31
Yeast-phase cell cycle of the polymorphic fungus Wangiella dermatitidis; Roberts RL et al.; The yeast-phase cell cycle of Wangiella dermatitidis was studied using flow microfluorimetry and the deoxyribonucleic acid (DNA) synthesis inhibitor hydroxyurea (HU) . Exposure of exponential-phase yeastlike cells to 0.1 M HU for 3 to 6 h resulted in the arrest of the cells in DNA synthesis and produced a nearly homogeneous population of unbudded cells . Treatment of the yeast-phase cells with HU for 9 h or longer resulted in the accumulation of the cells predominantly as budded forms having either a single nucleus in the mother cell or a single nucleus arrested in the isthmus between the mother cell and the daughter bud . Exposure of unbudded stationary-phase cells to 0.1 M HU resulted in the accumulation of the cells in the same phenotypes . Analysis by flow microfluorimetry and cell counts of HU-inhibited mithramycin-stained cells indicated that the eventual progress of HU-inhibited cells from unbudded to the two budded forms was due to the limited continuation of the growth sequence of the cell cycle even in the absence of DNA synthesis, nuclear division, and in some cases nuclear migration . On the basis of these observations and the results of flow microfluorimetric analysis of exponential-phase cells, a map of the yeast-phase cell cycle was constructed . The cycle appears to consist of two independent sequences of events, a budding growth sequence and a DNA division sequence . The nuclear division cycle of yeast-phase cells growing exponentially with a 4.5-h generation time is composed of a G1 interval of 148 min, as S phase of 16 min, and a G2 plus M interval of 107 min.

Genetics, 1980 Nov, 96(3), 613 - 25
Association of disomic chromosome loss with EMS-induced conversion in yeast; Campbell D; Experimental tests with the yeast Saccharomyces cerevisiae of a previously proposed model suggesting a causal relationship between disomic chromosome loss (n + 1 leads to n) and centromere-adjacent mitotic gene conversion were performed . Disomic haploid cells heteroallelic at two loci on the left arm of chromosome III were exposed to ethyl methanesulfonate (EMS) under nonlethal conditions; EMS-induced prototrophic gene convertants were selected and tested for coincident chromosome loss . The principal results are: (1) The frequency of chromosome loss among EMS-induced gene convertants selected to arise near the centromere is markedly enhanced over basal levels and remains constant, independent of EMS exposure . There is little such enhancement among EMS-induced convertants selected to arise far from the centromere . (2) Chromosome loss is almost completely associated with induced conversion of the centromere-proximal allele at the centromere-adjacent heteroallelic locus . This result is identical to (and confirms) results found previously for spontaneous loss-associated conversion . (3) The conversion polarity at the centromere-adjacent locus among unselected (nonloss-associated) induced or spontaneous mitotic convertants is identical to that among meiotic convertants and markedly favors the contromere-distal allele . These findings are wholly consistent with, and strengthen, the hypothesis that structural involvement of centromeric regions in nearby recombinational events may interfere with proper segregational function and lead to mitotic chromosome loss.

Eur J Biochem, 1980 Nov, 112(2), 283 - 91
Inhibition studies in situ of yeast catalases; Sels AA et al.; The catalase activity of the intact yeast cells towards external substrate is generally lower than the 'cryptic' activity which is revealed after cell lysis . The physiological basis for the reduced catalytic activity of the intact cell ('patent' activity) has been investigated by establishing the inhibition profiles of catalases in situ using selected probes; to this end we utilized either non-penetrating acids and/or catalase poisons able to cross the plasmic membrane . Owing to the peculiar features of the reaction mechanism, competitive inhibitors, which are known to interact with the prosthetic group of catalases, show an efficiency that is unlinked to the hydrogen peroxide concentration under the usual assay conditions ({H2O2} much less than Km) . This mode of interaction, which also characterizes the action of the penetrating probes HCOOH and HCN, is particularly well adapted to the study of the behaviour of the cytoplasmic catalases in situ . By this experimental approach, it has been shown that the catalase of the inner cellular region contributes, together with an isoenzyme present at the cell surface, to the patent activity . The mathematical processing of the data, which takes into account a rate-limiting diffusion of external substrate into the intact yeast cell, has allowed us to predict accurately the resulting apparent efficiency of inhibitors as a function of the physiological variations of the intracellular enzyme concentration.

Proc Natl Acad Sci U S A, 1980 Nov, 77(11), 6739 - 43
Replication and meiotic transmission of yeast ribosomal RNA genes; Brewer BJ et al.; The yeast Saccharomyces cerevisiae has approximately 120 genes for the ribosomal RNAs (rDNA) which are organized in tandem within chromosomal DNA . These multiple-copy genes are homogeneous in sequence but can undergo changes in copy number and topology . To determine if these changes reflect unusual features of rDNA metabolism, we have examined both the replication of rDNA in the mitotic cell cycle and the inheritance of rDNA during meiosis . The results indicate that rDNA behaves identically to chromosomal DNA: each rDNA unit is replicated once during the S phase of each cell cycle and each unit is conserved through meiosis . Therefore, the flexibility in copy number and topology of rDNA does not arise from the selective replication of units in each S phase nor by the selective inheritance of units in meiosis.

Cell, 1980 Nov, 22(2 Pt 2), 415 - 25
Mutations of the yeast SUP4 tRNATyr locus: transcription of the mutant genes in vitro; Koski RA et al.; Twenty-nine different SUP4-o tRNATyr genes with second-site mutations were transcribed in X . laevis cell-free RNA polymerase III transcription reactions, and the in vitro transcripts were analyzed by polyacrylamide gel electrophoresis . Nineteen mutant genes yield normal amounts of RNA that co-electrophorese with SUP4-o gene transcripts . RNA synthesized from a mutant gene lacing a single base pair migrated slightly faster in gels, as expected . The still shorter transcripts made from seven other mutant genes suggest that several mutations alter transcription starting or stopping points . Fingerprint analyses of transcripts from the two most extreme cases showed that premature termination occurred at new tracts of T residues resulting from the mutations . Two mutations significantly enhance transcription, and two mutations which alter the invariant C within the T psi CG sequence dramatically reduce SUP4-o gene transcription . The regions of the SUP4-o gene that surround these mutations are partially homologous to intragenic sequences in many other eucaryotic tRNA and 5S RNA genes . We hypothesize that these homologous sequences are recognized as promoter regions during RNA polymerase III transcription initiation.

Diabetes, 1980 Nov, 29(11), 919 - 25
Beneficial effect of chromium-rich yeast on glucose tolerance and blood lipids in elderly subjects; Offenbacher EG et al.; Twenty-four volunteers, mean age 78, including eight mildly non-insulin-dependent diabetics, were randomly allocated to one of two groups and were fed (daily for 8 wk) 9 g of either chromium-rich brewers' yeast (experimental) or chromium-poor torula yeast (control) . Before and after yeast supplementation, the serum glucose and insulin response to 100 g oral glucose was measured at 30 min intervals for 2 h . Fasting serum cholesterol, total lipids, and triglycerides were also determined . In the total experimental group (normals + diabetics) and in both the diabetic and nondiabetic experimental subgroups, glucose tolerance improved significantly and insulin output decreased after supplementation . Cholesterol and total lipids fell significantly after supplementation in the total experimental group . The cholesterol decrease was particularly marked in hypercholesterolemic subjects (cholesterol > 300 mg/dl) . In the control group, no significant change in glucose tolerance, insulin, triglycerides, or total lipids was found . Cholesterol was significantly lowered in the nondiabetic but not in the diabetic group . Thus, chromium-rich brewers' yeast improved glucose tolerance and total lipids in elderly subjects, while chromium-poor torula yeast did not . An improvement in insulin sensitivity also occurred with brewers' yeast supplementation . This supports the thesis that elderly people may have a low level of chromium and that an effective source for chromium repletion, such as brewers' yeast, may improve their carbohydrate tolerance and total lipids . The improvement in serum cholesterol in some control subjects, as well as in the total experimental group, also suggests the presence of a hypocholesterolemic factor other than chromium in both brewers' and torula yeast.

Proc Natl Acad Sci U S A, 1980 Nov, 77(11), 6541 - 5
Isolation of yeast genes with mRNA levels controlled by phosphate concentration; Kramer RA et al.; A library of DNA from the yeast, Saccharomyces cerevisiae, was constructed in phage lambda Charon 4 vector and then screened by differential plaque filter hybridization for genes induced by phosphate starvation . Two EcoRI fragments of 7.9 and 5.0 kilobase pairs that contained such genes were isolated . These cloned fragments may each carry one of the several copies of the genes for the repressible acid phosphatase of yeast . The fragments were use to examine mRNA levels of these genes in regulatory mutants of acid phosphatase.

Cell, 1980 Nov, 22(1 Pt 1), 291 - 8
Evidence for a physical interaction between the transposed and the substituted sequences during mating type gene transposition in yeast; Klar AJ et al.; Mating type switches in the yeast Saccharomyces cerevisiae occur by transposition of a replica of the "source" unexpressed loci HML and HMR to the mating type locus (MAT) . The incoming information replaces previously expressed DNA, resulting in an interconversion of MAT alleles . A strain of genotype HML alpha/HML alpha MAT alpha/mata-missense HMR alpha/hmra-nonsense HO/ho generates cells with the genotype HML alpha/HML alpha MAT alpha/MAT a HMR alpha/hmra-nonsense HO/ho; that is, wild-type MATa+ recombinants are produced efficiently by a strain in which the incoming a information and the resident mata allele bear different mutations . Production of the wild-type MATa recombinants requires the homothallism (switching) function, and the incoming a information and the resident mata allele must bear different mutations . This result is consistent with the formation of a heteroduplex between the incoming and the outgoing DNA at MAT . Thus a process of unidirectional gene conversion as a mechanism for mating type gene transposition is favored . A molecular model based on a single-strand transfer is proposed . Results also favor the idea that the direction of switching is controlled by cell's mating phenotype rather than by the genetic content of MAT.

Cell, 1980 Nov, 22(1 Pt 1), 277 - 89
Homothallic conversions of yeast mating-type genes occur by intrachromosomal recombination; Haber JE et al.; The switching of yeast mating-type alleles involves a transposition of a copy of a sequence from HML or HMR to replace the sequences at MAT . Using diploid strains of yeast we have discovered that about 1% of the homothalic conversions of MAT alleles are accompanied by large intrachromosomal rearrangements . These rearrangements are highly specific fusions of part of MAT either with HMR (to produce a deficiency ring chromosome) . We conclude that the mechanism of MAT conversions involves a highly specific pairing between the homologous sequences at MAT and the donor genes HML or HMR followed by a specialized gene conversion event, in which the original allele is replaced by a sequence copied from HMR or HML . At about a 1% frequency conversion of the MAT locus is accompanied by a reciprocal recombination event that results in an intrachromosomal deletion . This same preferential pairing is reflected in a high frequency (> 10(-3)) of site-specific mitotic recombination between MAT alleles on differenat chromosomes . A gene conversion model also allows us to explain the "illegal" transpositions of MAT alleles to HMR or HML that occur when normal excision of MAT is prevented.

Biochemistry, 1980 Oct 28, 19(22), 4967 - 72
Phenol hydroxylase from yeast: a lysyl residue essential for binding of reduced nicotinamide adenine dinucleotide phosphate; Neujahr HY et al.; The inducible enzyme phenol hydroxylase from Trichosporon cutaneum is a FAD-containing monooxygenase which catalyzes the NADPH-dependent hydroxylation of phenol to catechol . The enzyme contains 16 cysteinyl residues, 6--8 of which are essential for retention of FAD and for activity . The complete amino acid composition is now reported as well as the results of studies with amino group reagents . A number of amino group reagents inhibit the enzyme severely, most of them with a concomitant, more or less extensive release of FAD . P-pyridoxal inhibits the enzyme specifically, without affecting its FAD content . The P-pyridoxal modified enzyme has a characteristic absorption peak at 325 nm indicating the presence of a N epsilon-pyridoxyllysyl derivative . Such a derivative was identified in hydrolysates of the modified enzyme by means of column chromatography . The results obtained with P-pyridoxal-modified enzyme indicate that a lysyl residue is essential for activity by being involved in binding of the co-substrate NADPH . These results are corroborated by kinetic studies showing competition between P-pyridoxal and NADPH for the binding site . The reactivity of the essential lysyl residue toward P-pyridoxal is significantly increased in the presence of phenol . Inhibition by excess phenol shifts toward lower concentrations in the presence of P-pyridoxal . On the basis of the present results together with previous findings, we propose that phenol acts as a substrate effector by causing a conformation change which exposes a reactive lysyl residue with a concomitant burying of the essential SH groups and a tighter attachment of FAD.

J Biol Chem, 1980 Oct 25, 255(20), 9925 - 35
The transport of proteins into yeast mitochondria . Kinetics and pools; Ades IZ et al.; By double isotope pulse-labeling of yeast cells, we determined the kinetics of labeling at 9 degrees C of total mitochondrial membrane, mitochondrial matrix, and cytosolic proteins, the alpha, beta, and gamma subunits of F1 ATPase, and glyceraldehyde-3-phosphate dehydrogenase . We find that none of the mitochondrial proteins show a lag in the incorporation of label compared to cytosolic proteins . These results argue against the existence in the cytosol of large pools of mitochondrial proteins awaiting transport into the organelle . Cycloheximide addition during the pulse stops {35S}methionine incorporation into mitochondrial membrane and cytosolic proteins rapidly (approximately 1 min) and with identical kinetics . Compared to cytosolic protein, however, there is a persistent incorporation of label into mitochondria after a chase with cold methionine (t1/2 approximately 1.5 min at 9 degrees C) which cannot be accounted for solely by chain completion . We conclude that this continued incorporation reflects some transport process in addition to a completion of a round of translation . When cells are labeled during a synchronous "restart" of protein synthesis, where ribosome run-off from mRNA was first induced either by incubating cells for 4 h at 0 degrees C or by treatment with 5 mM aurintricarboxylic acid, the initial rate of incorporation of label into mitochondrial protein now lags behind that of cytosolic proteins . From these results and those in the accompanying report (Ades, I.Z., and Butow, R.A . (1980) J . Biol . Chem . 255, 9918-9924) we propose that the translation of mRNA specific for mitochondrial proteins takes place in the cytoplasm and that at least a portion of the polysomes are then transported and bind to the outer mitochondrial membrane, followed by completion of translation and transfer of the newly synthesized polypeptides into the mitochondria . From a consideration of all of the available data on protein transport into mitochondria in yeast, we conclude that cytoplasmic polysomes bound to the outer mitochondrial membrane function in the transport of proteins into mitochondria by a process not necessarily mutually exclusive of post-translational transport.

J Biol Chem, 1980 Oct 25, 255(20), 9918 - 24
The products of mitochondria-bound cytoplasmic polysomes in yeast; Ades IZ et al.; Experiments were undertaken to examine the fate and composition of polypeptides synthesized on cytoplasmic polysomes associated with the outer mitochondrial membrane of Saccharomyces cerevisiae . Mitochondria with their associated cytoplasmic polysomes were isolated from growing yeast spheroplasts and placed in a polypeptide chain completion system together with {35S}methionine . Of the total products synthesized in the readout system, 80 to 85% remain associated with the mitochondria after sucrose gradient centrifugation . Most of the labeled products are resistant to papain digestion unless the membranes are disrupted by treatment with detergent or shaking with glass beads . When free cytoplasmic polysomes were translated in the presence of {35S}methionine and incubated with mitochondria, only about 20% of the labeled polypeptides remain associated with the mitochondria; furthermore, most of these products are equally sensitive to papain digestion in the presence or absence of detergent . These results support the view that the cytoplasmic polysomes associated with the outer mitochondrial membrane of yeast facilitate the segregation of newly synthesized proteins into the organelle . The proportion of the alpha, beta, and gamma subunits of the F1-ATPase was determined among the products synthesized by mitochondria-bound and free cytoplasmic polysomes . By double antibody precipitation and immunoreplicate electrophoresis, we find that the proportion of the subunits of F1-ATPase is much greater among the products of the mitochondria-bound polysomes than those synthesized on free polysomes.

Nucleic Acids Res, 1980 Oct 24, 8(20), 4651 - 69
Inverted repeated sequences in yeast nuclear DNA; Klein HL et al.; The inverted repeated sequences (foldback DNA) of yeast nuclear DNA have been examined by electron microscopy and hydroxyapatite chromatography . Of the inverted repeat structures seen in the electron microscope, 34% were hairpins and 66% had a single stranded loop at the end of a duplex stem . The number average length of the repeat was 0.3 kb and the single stranded loop was 1.6 kb . It is estimated that there are approximately 250 inverted repeats per haploid genome . A statistical analysis of the frequency of molecules containing multiple inverted repeats showed that these sequences are non-randomly distributed . The distribution of inverted repeats was also examined by measuring the fraction of total DNA in the foldback fraction that bound to hydroxyapatite as a function of single strand fragment size . This analysis also indicated that the inverted repeats are clustered . Renaturation kinetic analysis of isolated foldback and inverted repeat stem sequence DNA showed that these sequences are enriched for repetitive DNA.

Nature, 1980 Oct 23, 287(5784), 750 - 2
Dimeric tRNA precursors in yeast; Schmidt O et al.; Two DNA fragments, each containing tRNA(Arg)3 and a tRNA(Asp) gene in close conjunction, have been isolated from different genomic regions of Saccharomyces cerevisiae . Nucleotide Nucleotide sequence analysis of the gene regions revealed that in both fragments the tRNA(Arg)3 coding region is located 5'-proximal to the tRNA(Asp) coding region . They are separated by an identical spacer of 10 nucleotides . Although the 5'-flanking sequences are different in the two plasmids, some similarities are observed . To test the mode of expression of this gene configuration, we transcribed the DNA fragments in a Xenopus oocyte nuclear extract . Specific transcription of the yeast tRNA genes took place in an RNA precursor which comprised both tRNA species . We report here that the precursor RNA was processed to the mature-sized tRNA molecules, indicating the presence of an enzyme activity in the Xenopus nucleus capable of cutting a dimeric tRNA precursor . This is the first observation of a eukaryotic dimeric tRNA precursor.

Experientia, 1980 Oct 15, 36(10), 1149 - 50
Inactivation of yeast glucose-6-P dehydrogenase by aspirin; Han PF et al.; Glucose-6-P dehydrogenase is irreversibly inactivated by treatment with Na salts of aspirin . Kinetic data show that 1 molecule of aspirin reacts with each active unit when the enzyme is inactivated . The rate of inactivation is enhanced with increasing pH but is reduced in the presence of glucose-6-P or NADP+ . Na salicylate fails to inactivate the enzyme.

J Biol Chem, 1980 Oct 10, 255(19), 9388 - 98
Affinity labeling of the active site of yeast pyruvate kinase by 5'-p-fluorosulfonylbenzoyl adenosine; Likos JJ et al.; Yeast pyruvate kinase is irreversibly inactivated by 1.1 mM 5'-p-fluorosulfonylbenzoyl adenosine at pH 8.6 with an initial rate constant of 0.019 min-1 . A plot of kinact versus the 5'-p-fluorosulfonylbenzoyl adenosine concentration yields a hyperbolic curve indicative of binding of the analog prior to reaction . Marked protection is afforded by phosphoenolpyruvate + fructose 1,6-diphosphate + Mg2+ or MgATP suggesting that reaction occurs within the active site . When assayed at less than saturating phosphoenolpyruvate concentrations, the inactivation caused by the reagent in the absence of added ligands appears slower, and reaction in the presence of phosphoenolpyruvate, fructose 1,6-diphosphate, and Mg2+ produces an activation of the enzyme, the extent of which is dependent on the assay concentration of phosphoenolpyruvate . The rate constant for activation was observed to be 0.113 min-1 . The activated enzyme exhibits both a lowered K0.5 and Hill coefficient compared to native pyruvate kinase . Subsequent addition of 5'-p-fluorosulfonylbenzoyl adenosine to activated pyruvate kinase in the absence of added ligands leads to inactivation with the rate constant independent of the assay concentration of phosphoenolpyruvate . Covalent reaction of pyruvate kinase with 5'-p-fluorosulfonylbenzoyl adenosine thus occurs at two distinct sites . In the presence of phosphoenolpyruvate, fructose 1,6-diphosphate, and Mg2+, incorporation of tritiated 5'-p-fluorosulfonylbenzoyl adenosine is linearly proportional to the extent of activation of the enzyme, with 4 mol of reagent bound/mol of tetrameric pyruvate kinase for maximally activated enzyme . In the absence of added ligands, approximately 4.5 mol of reagent are incorporated/mol of enzyme at 15 min of reaction, while 80% of the original activity remains . Subsequent incorporation is proportional to the extent of inactivation with 8 mol bound at 100% in activaton . In the presence of phosphoenolpyruvate, fructose 1,6-diphospate, and Mg2+, 3 tyrosines and 1 lysine residue, and in the absence of ligands, 6 tyrosines and 2 lysine residues are modified, suggesting that both amino acids are within the two nucleotide sites.

J Biol Chem, 1980 Oct 10, 255(19), 9501 - 6
Transcription and in vitro processing of yeast 5 S rRNA; Tekamp PA et al.; A method is described for the isolation of a yeast chromatin fraction highly enriched in ribosomal DNA sequences . In the presence of exogenous yeast RNA polymerase III, this purified chromatin actively synthesizes a set of 5 S ribosomal RNAs all of which have 5'-sequences identical with mature 5 S RNA but which end with a variable number (up to 10) of additional residues at the 3'-terminus . These extra nucleotides are precisely removed by a processing nuclease found in the chromatin supernatant fraction.

J Biol Chem, 1980 Oct 10, 255(19), 9262 - 7
The pH and temperature dependence of the activity of the high Km cyclic nucleotide phosphodiesterase of bakers' yeast; Londesborough J et al.; The hydrolysis of adenosine 3':5'-monophosphate by the high Km cyclic nucleotide phosphodiesterase of bakers' yeast was studied over a range of temperature and pH at I = 0.17 . The effects of ionic strength and MgCl2 concentration were studied at pH 7.7 and 30 degrees C . Km and Vmax were insensitive to changes in the MgCl2 concentration between 1 and 30 mM, implying that this enzyme (which does not require free divalent metal ions) does not discriminate between free cyclic AMP- and the Mg-cyclic AMP+ complex . Vmax decreased below pH 6.8 because of protonation of a group required in the basic form in the enzyme x substrate complex . On the basis of its pK (5.46 at 30 degrees C) and delta H (23 kJ/mol) this group was tentatively identified as imidazole . Vmax/Km decreased above pH 6.8 because of ionization of a group required in the acid form in the free enzyme, with a pK of 7.88 at 30 degrees C and a delta H of about 13 kJ/mol . Several possibilities exist for the identity of this group, the most likely being a second imidazole, sulfhydryl, or a water molecule bonded to tightly bound zinc . At pH 7.90, log Vmax and log Km both changed linearly with 1/T (between 12 degrees C and 37 degrees C) with enthalpies of 47 and 55 kJ/mol, respectively . Consequently, at low enough cyclic AMP concentration, the rate of reaction at pH 7.90 decreases slightly when the temperature is increased . This is also true at higher pH, but in the physiological pH range (6.4 to 7.5) Vmax/Km and, therefore, the rate of reaction at very low cyclic AMP concentration were nearly independent of temperature . Under physiological conditions, the Km approaches the upper limit of in vivo cyclic AMP concentrations in yeast, and at normal in vivo cyclic AMP concentrations the pH optimum is within or below the physiological range of pH in yeast.

Nature, 1980 Oct 9, 287(5782), 504 - 9
Isolation of a yeast centromere and construction of functional small circular chromosomes; Clarke L et al.; The centromeric DNA (CEN3) from yeast chromosome III has been isolated on a 1.6 kilobase-pair segment of DNA located near the centromere-linked CDC10 locus of Saccharomyces cerevisiae . When present on a plasmid carrying a yeast chromosomal replicator, CEN3 enables that plasmid to function as a chromosome both mitotically and meiotically . Minichromosomes containing CEN3 are stable in mitosis and segregate as ordinary yeast chromosomes in the first and second meiotic divisions.

Biochim Biophys Acta, 1980 Oct 3, 592(3), 377 - 84
Classification of nucleotide binding sites on mitochondrial F1-ATPase from yeast; Recktenwald D et al.; Methods are described to classify nucleotide binding sites of the mitochondrial coupling factor F1 from yeast on the basis of their affinities and stability properties . High affinity sites or states for ATP and related adenine analogs and low affinity sites or states which bind a broad range of different nucleotide triphosphates are found . The results are discussed in terms of a two site, two cycle scheme, where binding of nucleotide at one site facilitates the release of nucleotide at a second site.

Biokhimiia, 1980 Oct, 45(10), 1881 - 5
{Heterogeneity of the amino acid pool of the yeast cell with respect to the rate of carbon reduction}; Davidova EG et al.; A new procedure for estimating the correlation between the metabolic and relatively stable carbon depots in the amino acid pool of the yeast cell is proposed . It has been shown that the metabolic carbon depot of the amino acid pool of the yeast cell utilizing glucose as the only carbon source makes up to 9.3% of the total carbon of this pool or 0.92% of total carbon of the cell.

Eur J Biochem, 1980 Oct, 111(2), 491 - 501
Membrane mutants: a yeast mutant with a lesion in phosphatidylserine biosynthesis; Kovac L et al.; A single-gene nuclear choline-requiring mutant of Saccharomyces cerevisiae was studied . Choline as a growth supplement to synthetic media could be substituted by low concentrations of dimethylethanolamine, monomethylethanolamine or ethanolamine . DL-Serine also supported growth, but only at high concentrations: on a molar basis it was approximately one hundred times less effective than choline . When cultured in unsupplemented medium the mutant cells soon ceased to grow . The growth-arrested cells contained less than one fifth of the phosphatidylethanolamine present in wild-type cells and only traces of phosphatidylserine . The relative content of the two phospholipid species was raised by growing the mutant cells in the presence of choline of the other supplements but still remained lower than in wild-type cells . The mutant cells depleted of phosphatidylethanolamine and phosphatidylserine had greatly diminished ability to fuse with other cells in mating and their protoplasts showed increased resistance to hypotonic lysis . Respiration was not substantially affected by the deficit of the two phospholipid species in the mutant . In cell-free preparations, the affinity of the phosphatidylserine synthesizing system for serine was found to be almost two orders of magnitude lower in the mutant than in the wild-type . The impairment of phosphatidylserine synthesis accounts for growth requirement and the abnormal phospholipid composition of the mutant cells.

Eur J Biochem, 1980 Oct, 111(1), 79 - 87
Yeast mutants defective in acetyl-coenzyme A carboxylase and biotin: apocarboxylase ligase; Mishina M et al.; Among more than 7000 mutants of Saccharomyces cerevisiae, requiring saturated fatty acids, 61 acetyl-CoA-carboxylase-deficient strains have been identified . According to their mutual complementation characteristics these mutants have been assigned to two different genes, acc1 and acc2 . Both acetyl-CoA carboxylase genes are unlinked to each other and to the fatty acids synthetase genes fas1 and fas2 . The acetyl-CoA carboxylases of several acc1 and acc2 mutants have been purified and assayed for their overall and component enzyme activities . Besides overall acetyl-CoA carboxylation, which was lost in all cases, both component enzymes, biotin carboxylase and transcarboxylase, were simultaneously affected in most mutants, though often to a different relative extent . Similarly, the comparison of biochemical and genetic complementation data revealed no basis for a clear distinction between specific biotin carboxylase and transcarboxylase mutants . These results suggest that acc1 is a cluster gene coding for a multifunctional protein harboring both acetyl-CoA carboxylase component enzyme activities on the same polypeptide chain . The acetyl-CoA carboxylase isolated from acc2 mutants was free of biotin . Correspondingly, biotin:apoacetyl-CoA-carboxylase ligase activity was missing in acc2 mutants . Therefore, it is concluced that the primary defect in acc2 mutants is in the biotin:apocarboxylase ligase . In agreement with this conclusion, the acc2 acetyl-CoA carboxylase can be activated, in the presence of biotin and ATP, by ligase preparations from wild-type or acc1 mutant cells . By the use of these mutants, evidence was obtained that in vivo the biotinylation of both acetyl-CoA carboxylase and pyruvate carboxylase is catalyzed by the same ligase.

C R Seances Acad Sci D, 1980 Sep 29, 291(4), 393 - 6
{Crystallization of the complex formed between yeast aspartyl tRNA and its specific aminoacyl tRNA synthetase}; Giege R et al.; The crystallization of the complex formed between aspartic acid tRNA from the yeast Saccharomyces cerevisiae and homologous aspartyl-tRNA synthetase is described . Crystals were obtained, using the vapour phase diffusion technique and ammonium sulphate as the precipitant agent.

Science, 1980 Sep 19, 209(4463), 1396 - 400
Directed deletion of a yeast transfer RNA intervening sequence; Wallace RB et al.; Many eukaryotic genes contain intevening sequences, segments of DNA that interrupt the continuity of the gene . They are removed from RNA transcripts of the gene by a process known as splicing . The intervening sequence in a yeast tyrosine transfer RNA (tRNA Tyr) suppressor gene was deleted in order to test its role in the expression of the gene . The altered gene and its parent were introduced into yeast by transformation . Both genes exhibited suppressor function, showing that the intervening sequence is not absolutely essential for the expression of this gene.

Science, 1980 Sep 19, 209(4463), 1380 - 4
Recombination of dispersed repeated DNA sequences in yeast; Scherer S et al.; Yeast transformation can be used to insert new sequence arrangements into a variety of chromosomal locations by homologous recombination . These newly inserted sequences can recombine with similar sequences located on other chromosomes . In these events, information is duplicated without being lost at the site from which it is derived . Similar mechanisms might be utilized by cells to provide new functions during development or differentiation.

Science, 1980 Sep 19, 209(4463), 1375 - 80
The origins of gene instability in yeast; Roeder GS et al.; Two unstable mutations at the his4 locus of yeast are due to the insertion of the transposable elements Ty912 and Ty917 into the his4 regulatory region . The two transposons are related, one being derived from the other by a substitution of 4000 base pairs of DNA . Element Ty912 includes identical terminal repeats, whereas the terminal repeats of Ty917 are not identical . Transposition of Ty912 or Ty917 generates 5-base-pair duplications of the target DNA at either end of the element . Expression and reversion of a his4 gene containing Ty912 or Ty917 is controlled by three unlinked regulatory genes . The properties of these regulatory genes are similar to those described for the controlling elements in maize.

Biochim Biophys Acta, 1980 Sep 19, 609(2), 329 - 41
Biogenesis of mitochondria . Two-dimensional electrophoretic analysis of mitochondrial translation products in yeast; Stephenson G et al.; 1 . Mitochondrial translation products of yeast Saccharomyces cerevisiae were separated according to charge as well as molecular weight by a highly resolving two dimensional electorphoretic technique (isoelectric focusing in the first dimension ana SDS-electrophoresis in the second dimension) . 2 . The major protein components (the oligomeric form of subunit 9 of mitochondrial ATPase, var 1, cytochrome oxidase subunits I, II and III, subunit 6 of mitochondrial ATPase and cytochrome b apoprotein) were identified either from their mobility in SDS-electrophoresis or by using mit- mutants defective in certain mitochondrially made polypeptides . 3 . This method allowed the separation of subunit III of cytochrome oxidase and subunit 6 of mitochondrial ATPase which cannot be resolved by conventional SDS-polyacrylamide gel electrophoresis . 4 . Subunit II of cytochrome oxiodase resolves in two spots of similar pI values and subunit 6 of mitochondrial ATPase resolves in two spots of similar molecular weight . In both cases the double spots disappear simultaneously following a single mutation in the coresponding structural gene . 5 . Total mitochondrial proteins were also resolved two-dimensionally revealing over 100 components . The mitochondrial translation products, with the exception of subunit 9 of mitochondrial ATPase, could be easily recognized among the other mitochondrial proteins.

Nucleic Acids Res, 1980 Sep 11, 8(17), 4021 - 39
Serine activation is the rate limiting step of tRNASer aminoacylation by yeast seryl tRNA synthetase; Dibbelt L et al.; Using the quenched flow technique the mechanism of seryl tRNA synthetase action has been investigated with respect to the presteady state kinetics of individual steps . Under conditions where the strong binding sites of the enzyme are nearly saturated and the steady state turnover number is about 1 s-1, rate constants of four different processes have been determined: steps connected with substrate associations are relatively slow (12 s-1 for the entire process); activation of serine is the rate determining step (about 1.2 s-1 in presence of tRNASer); whereas the transfer of serine onto tRNASer (35 s-1) and the dissociation of seryl tRNASer (70 s-1) are fast . Similar kinetic parameter seem to hold also for the steady state reactions . This conclusion is based on a detailed study of the substrate, product, and Mg2+ concentration dependence of the transfer reaction . The results also indicate that a second serine binding site is operative . Since the transfer of serine from a preformed adenylate complex onto tRNASer is fast, seryl adenylate seems to be a kinetically competent intermediate of the aminoacylation reaction although, of course, alternative mechanisms cannot be excluded.

Biochim Biophys Acta, 1980 Sep 9, 615(1), 187 - 98
Interaction of proteinases and their inhibitors from yeast . Activation of carboxypeptidase Y; Fischer EP et al.; In a crude extract of baker's carboxypeptidase Y is predominantly found in an inactive form . A procedure for the isolation of the inactive form of the enzyme is presented . It is shown that the inactive form is identical to the reconstituted complex of carboxypeptide Y with its inhibitor . This complex is stable above pH 5, i.e., it remains inactive between pH 5 and 9 . The conversion to the active enzyme occurs below pH 5, also in the absence of proteolytic enzymes . The inhibitor of carboxypeptidase Y can be removed enzymatically from the complex by treatment with proteinase B (EC 3.4.22.9) at pH 7 . At pH 5, the carboxypeptidase Y-inhibitor complex is activated both by proteinase A (EC 3.4.23.6) and B . Yeast proteinases are activated in a crude extract by incubation at pH 5 {3} . Based on the levels of proteinase A and B in an activated extract and on the time required for conversion to active carboxypeptidase Y, proteinase B is at least 10-times more effective than proteinase A . Peptides that arise during the pH 5-incubation procedure did not accelerate the proteolytic activation of carboxypeptidase Y . The inhibitor of carboxypeptidase Y is completely degraded in the proteolytic activation steps, no accumulation of intermediates is observed . Only one form of active carboxypeptidase Y is found to be present in the proteolytically activated extracts, i.e., no polypeptide fragments of carboxypeptidase Y-inhibitor remain bound to the enzyme after it has been activated by proteinase B . In vacuoles prepared from spheroplasts no inactive carboxypeptidase Y can be detected.

Biochim Biophys Acta, 1980 Sep 9, 615(1), 132 - 42
Effects of glucose and magnesium ion on the quenching of yeast hexokinase fluorescence by acrylamide; Feldman I et al.; To probe the effects of the substrate, glucose, and the cofactor, Mg2+, on the structure of hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1), titrations of the tryptophan fluorescence of yeast hexokinase isozyme P-II(B) were performed . Acrylamide was used as a quenching titrant in the absence and in the presence of glucose and Mg2+ singly and together at pH 5.5 and 8.3 at 20 degrees C . The four tryptophan residues of the monomeric subunit of yeast hexokinase may be classified as two surface residues, one being highly accessible to dissolved I- and one with restricted accessibility to I-, one glucose-quenchable residue in the cleft, and one buried (Kramp, D.C . and Feldman, I . (1978) Biochim . Biophys . Acta 537, 406--416) . The acrylamide data were analyzed by least-squares computer analysis for quenching constants and fractional fluorescence values of the tryptophan residues . The quenching constants measure the accessibilities of the residues to the quencher, while the fractional fluorescences are related to the microenvironments of the fluorophores . At each pH value, glucose altered the quenching constants, but not the fractional fluorescence, of the tryptophan residues . Mg2+ greatly accentuated at this glucose effect, especially for the surface residue near the cleft opening . Comparison of acrylamide- and I-quenching data shows that this particular residue has a positively charged microenvironment . A pH change from 5.5 to 8.3 increased the acylamide-accessibility of the cleft tryptophan but did not seem to influence accessibility of the surface residues or the buried residue significantly, thus strengthening our previous conclusion that the cleft opening is small enough at pH 5.5 to partially restrict entrance of organic molecules and negative ions . However, with saturating glucose present there was a pH effect on the surface residue accessibility . Titrations in 55 vol.% glycerol suggest the presence of transient channels (not just holes) in the hexokinase structure, which allows penetration of the protein by solution . Consequently, the buried tryptophan residue is quenched more strongly by dissolved acrylamide than is attributable to diffusion of quencher through the protein matrix.

Cell, 1980 Sep, 21(2), 501 - 8
Replication and recombination functions associated with the yeast plasmid, 2 mu circle; Broach JR et al.; By examining both the transformation efficiency of yeast of various plasmids containing defined regions of the 2 mu circle genome and the characteristics of the resultant transformants, we have identified several regions of the 2 mu circle genome which are involved in 2 mu circle replication or recombination . First, by identifying those DNA fragments from the molecule which promote high frequency transformation of yeast, we have localized the origin of replication to a sequence partially within the large unique region, which, as determined by subsequent deletion analysis, extends from the middle of the inverted repeat region into the contiguous unique region . Second, by examining the relative efficiency of replication in yeast of hybrid plasmids containing either the entire 2 mu circle genome or a fragment of 2 mu circle encompassing the origin of replication, we have determined that efficient use of the 2 mu circle origin requires some function or functions encoded in the molecule at a site away from the origin . Third, by examining the ability of a mutant 2 mu circle molecule to undergo intramolecular recombination in yeast, we have identified a 2 mu circle gene which codes for a product required for this process.

Int J Radiat Biol Relat Stud Phys Chem Med, 1980 Sep, 38(3), 267 - 75
Synthesis of inducible enzymes in irradiated yeast cells: inhibition by ionizing radiation; Kiefer J et al.; The induced activity of the enzyme arginase was measured in diploid wild type Saccharomyces cerevisiae after X-ray and 241Am-alpha-particle exposure . It was found that after doses which are comparable to those necessary to reduce survival, little effect on enzyme activity is seen immediately after irradiation but it is reduced on further incubation . In this case there is an oxygen enhancement ratio of about 2 as for survival . Suppression immediately after exposure requires considerably higher doses, and no oxygen effect is seen . To achieve the same effect with alpha-particles requires even higher doses, the apparent r.b.e . is about 0 . 1 . X-ray damage to induced enzyme activity is subject to liquid holding recovery . The results are discussed in relation to current theories of gene inactivation by ionizing radiation.

Eur J Biochem, 1980 Sep, 110(1), 67 - 76
The histones of yeast . The isolation and partial structure of the core histones; Brandt WF et al.; The four core histones of yeast chromatin have been isolated . Amino acid composition, electrophoretic mobility and partial sequences identify one variant each of the histones H3 and H4, whereas the histones H2A and H2B are represented by two variants each . In the yeast histones H3 and H4 7% of the residues, positioned in the partial sequences vary if compared with the corresponding histones from higher plants and animals, for the histones H2A and H2B from yeast this figure is 20%.

Proc Natl Acad Sci U S A, 1980 Sep, 77(9), 5380 - 4
Preferential inclusion of extrachromosomal genetic elements in yeast meiotic spores; Brewer BJ et al.; During meiosis and sporulation in the yeast Saccharomyces cerevisiae, extrachromosomal traits are efficiently transmitted to haploid spores . Although the pattern of inheritance of chromosomal traits reflects the mechanism of regular chromosomal segregation in meiosis, it is not known what processes are reflected by the efficient inheritance of extrachromosomal traits . Because extrachromosomal genetic elements in yeast are present in multiple copies, perpetuation of an extrachromosomal trait could occur by the passive envelopment of a subset of copies or by an active sequestering of all or a subset of copies within the four spores . We show that only subsets of the four extrachromosomal nucleic acids commonly found in yeast are transmitted through meiosis--55% of mitochondrial DNA copies, 82% of the 2-micron DNA plasmids, and about 70% of the L and M double-stranded RNAs . However, electron micrographs of serial sections through yeast asci indicate that the four spore enclose only 30% of the total ascus material . Thus these extrachromosomal elements are preferentially included within the spores, indicating that their inheritance is not a random process . Transmission of mitochondrial DNA can be accounted for by the observed enclosure of 52% of the mitochondrial volume within the spores . The high transmission frequencies of the double-stranded RNAs (which exist as virus-like particles in the cytoplasm) and 2-micron DNA must indicate that either these nucleic acids are actively recruited from the cytoplasm by some mechanism or they are associated in some way with the nucleus during meiosis.

Eur J Biochem, 1980 Sep, 110(1), 189 - 96
Cytochrome c interaction with yeast cytochrome b2 . Heme distances determined by energy transfer in fluorescence resonance; Vanderkooi JM et al.; Fluorescent derivatives of cytochrome c were prepared by replacing the heme iron with closed-shell metals such as zinc or tin . The iron-free derivatives of cytochrome c bind to yeast lactate dehydrogenase (cytochrome b2) stoichiometrically and with high affinity . Spectral overlap exists between the fluorescence of porphyrin, Zn(II) or Sn(IV) cytochrome c and the absorption of the heme of cytochrome b; therefore dipole-dipole interaction is possible as predicted by Forster's theory of energy transfer . Changes in the fluorescence yield and the fluorescent decay profile of the cytochrome c derivatives are consistent with the view that the heme distance is sufficiently close for dipolar interactions . The distance calculated from the data depends upon assumptions in the theory for energy transfer and uncertainties in the experiment . It can be argued that due to the symmetry of the metalloporphyrins the relative orientations of the two hemes do not introduce a significant uncertainty in the calculation . However the decay profiles of the iron-free cytochromes are complex, possibly reflecting structural rearrangement of the polypeptide chain during the fluorescent lifetime . The steady-state fluorescent yields would indicate that the mean distance is around 1.8 nm.

Eur J Biochem, 1980 Sep, 110(2), 431 - 7
An endonuclease from yeast mitochondrial fractions; Morosoli R et al.; A membrane-bound endonuclease has been isolated from mitochondrial fractions of Saccharomyces cerevisiae . The enzyme is present in a stable complex and has an approximate molecular weight of 14 000 . It requires Mg2+ or Mn2+ for activity, and has an optimum pH of 7.0 . Its activity with native DNA is five times less than with denatured DNA in 0.05 M KCl and is very low in 0.2 M KCl . The activity with RNA is 40% of that with denatured DNA; the two substrates are competitive . Its mode of action is endonucleolitic, cuts both strands of native lambda DNA at the same or nearby sites . After mild digestion of DNA, analysis of 5'-end groups of the digestion products indicated a marked preference for deoxythymidylic and deoxyguanilic acid residues as the site of enzymatic cleavage . After exhaustive digestion of DNA, mononucleotides (2.4%), dinucleotides (70.5%) and trinucleotides (27%) ending in 5'-phosphate are produced.

Biokhimiia, 1980 Sep, 45(9), 1568 - 75
{Affinity labeling of inorganic pyrophosphatase from yeast by methylphosphate}; Lagutina IO et al.; Yeast inorganic pyrophosphatase is specifically and irreversibly inactivated by methylphosphate . The high rate of inhibition, the protective effect of the substrate, the strict correlation between the degree of inhibition and the amount of the protein-bound reagent and the effect of saturation of the enzyme with methylphosphate provide evidence in favour of the reaction in the active center . Modification of two chemically identical enzyme subunits proceeds at different rates and results in a formation of phosphorylated subunits with different stability of the phosphate bond, which is indicative of the mutual effects of the pyrophosphatase subunits . The reaction between the modified enzyme and hydroxylamine suggests that the interaction between pyrophosphatase and methylphosphate entails modification of the carboxylic groups of two active centers, resulting in a formation of the acylphosphate bonds.

Nature, 1980 Aug 28, 286(5776), 860 - 5
Nucleotide sequence of the yeast plasmid; Hartley JL et al.; The nucleotide sequence of the yeast DNA plasmid (2 mu circle) from Saccharomyces cerevisiae strain A364A D5 has been determined . The plasmid contains 6,318 base pairs, including two identical inverted repeats of 599 base pairs . Possible functions are suggested, and attributes of an improved vector for cloning foreign DNAs in yeast are discussed.

J Biol Chem, 1980 Aug 25, 255(16), 7740 - 5
Stimulation of in vitro mitochondrial protein synthesis by yeast cytoplasmic extracts is caused by guanyl nucleotides; Ohashi A et al.; Micromolar concentrations of GDP or GTP stimulate protein synthesis by isolated yeast mitochondria 3- to 10-fold even if alpha-ketoglutarate and an ATP-regenerating system are present . No stimulation is observed with GMP, UTP, CTP, TTP, and the nonhydrolyzable GTP analogues guanyl(beta, gamma-methylene) diphosphate and guanyl imidodiphosphate . This stimulatory effect of exogenously added guanyl nucleotides may answer the long standing question why protein synthesis by isolated mitochondria is so slow . It can also explain previous reports by two other laboratories that a high speed supernatant from yeast cells stimulates protein synthesis by isolated mitochondria . The supernatant contains nondialyzable GMP which is converted to GDP under the conditions used for assaying mitochondrial protein synthesis . The stimulatory effect of high speed supernatants is abolished by 5'-nucleotidase (which degrades GMP) or by trypsin (which destroys supernatant protein(s) necessary for converting GMP to GDP) . No evidence was obtained that the stimulatory effect of high speed supernatants was caused by precursors to cytoplasmically made cytochrome c oxidase subunits.

J Biol Chem, 1980 Aug 10, 255(15), 7181 - 91
Formation of an iso-1-cytochrome c-like species containing a covalently bonded heme group from the apoprotein by a yeast cell-free system in the presence of hemin; Basile G et al.; Incubation of the 125I-labeled apoprotein, prepared from 125I-labeled iso-1-cytochrome c, with a yeast mitochondrial fraction in the presence of hemin, NADPH, and an extract of the postmitochondrial fraction at 32 +/- 1 degree C for 30 min has resulted in formation of cytochrome c-like species in yields of up to 35% . This radioactive synthesized species contains a functional group which responds to reduction with ascorbate and oxidation with K3Fe(CN)6 in that it is resistant in the reduced form and susceptible in the oxidized form to trypsin action in a manner characteristic of native cytochrome c . The functional group cannot be removed from the protein by cold HCl-acetone or 8 M urea treatment . The reduced form of the synthesized species exhibits resistance against autoxidation and the oxidized form can be reduced also by cytochrome b2 . The synthesized species exhibits the same compact hydrodynamic volume of native cytochrome c . Treatment with silver sulfate followed by incubation with dithiothreitol converts the synthesized species to the original apoprotein as judged by an increase in the hydrodynamic volume . Thus, the synthesized species is indistinguishable from the original labeled iso-1-cytochrome c by these measurements; i.e . the synthesized species consists of the apoprotein to which heme is covalently attached through the thioether bond(s) . The active factor of the mitochondrial fraction is heat-labile . The synthetic activity is strongly dependent on pH with a maximum approximately at pH 7.0 . Hemin (or heme) appears to be required for this synthesis . The postmitochondrial fraction is inactive by itself . However, its addition markedly increases the synthetic activity . This factor is heat-stable, soluble in 80% methanol (or 75% ethanol), and insoluble in ethyl ether or ethyl acetate . Addition of NADP(H) (or NAD(H)) also increases the synthetic activity, the reduced form being more effective than the oxidized form . The postmitochondrial factor and the pyridine nucleotides appear to enhance the effect of each other . Thus, it seems that cytochrome c or a cytochrome c-like species is formed from the apoprotein and heme (or hemin) by an enzyme, cytochrome c synthetase, present in mitochondria.

Biochim Biophys Acta, 1980 Aug 7, 614(2), 225 - 36
Flow kinetics of yeast alcohol dehydrogenase attached to nylon tubing; Mazid MA et al.; Yeast alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was attached covalently to the inner surface of nylon tubing, and the immobilized enzyme retained its activity over a period of months . A study was made of the flow kinetics for the reaction between ethanol and NAD . With the ethanol held at saturating concentrations there was partial diffusion control, the extent decreasing with increasing flow rate and increasing NAD concentration . With the NAD at saturating concentrations there was no appreciable diffusion control . The apparent Michaelis constants varied with flow rate vf, being linear in vf-1/3, and extrapolation to infinite flow rate (vf-1/3 = 0) gave the intrinsic Michaelis constants . The inhibition by products was also studied . The results for both NADH and acetaldehyde showed mixed competitive and non-competitive inhibition, with a preponderance of the former . Acetaldehyde is the stronger inhibitor, and this is consistent with the lack of dissusion control with variable ethanol . Inhibition by acetaldehyde is not affected by flow rate, but inhibition by NADH is affected, presumably because of the greater degree of diffusion control with variable NAD.

Biochim Biophys Acta, 1980 Aug 7, 614(2), 601 - 6
Subunit specificity of the two acetyl-CoA synthetases of yeast as revealed by an immunological approach; Satyanarayana T et al.; 1 . In the present paper, the two acetyl-CoA synthetases (acetate:Coenzyme A ligase (AMP-forming), EC 6.2.1.1) elaborated under aerobic or nonaerobic conditions are further differentiated by an immunological approach . 2 . The subunit of the aerobic isozyme was prepared and found to be homogeneous by disc gel electrophoresis in the presence of sodium dodecyl sulfate (SDS) and by ultracentrifugal studies . An s20,w of 3.6 and an apparent molecular weight of 80,500 +/- 500 were calculated for this subunit . 3 . The subunit was precipitated by antibody prepared against the aerobic enzyme . Antibody prepared against the subunit also reacted in precipitin tests with the subunit, but not with the native enzyme . The latter antibody nevertheless inhibited the native enzyme but not the nonaerobic isozyme.

Poult Sci, 1980 Aug, 59(8), 1807 - 11
Blood constituents of yeast fed chicks; Saoud NB et al.; Two experiments on broiler chicks raised to 4 weeks of age were carried out to study the effects of replacing soybean protein in a semisynthetic diet with yeast protein from molasses (CEPAH) . Criteria measured were body weight, feed efficiency, plasma urea nitrogen, serum uric acid, serum total protein, albumin, globulin and albumin-globulin ratios . Analysis of the data showed that yeast protein produced from molasses depressed growth and feed efficiency at levels 10, 15, and 20% of the diet . The effects of yeast protein on blood nitrogenous constituents were variable and not significant, but in general, the inclusion of yeast protein caused an increase in serum albumin and a decrease in serum globulin resulting in a higher albumin-globulin ratio . The changes observed in blood nitrogenous constituents in this study do not explain all the detrimental effects of yeast protein on growth and feed efficiency of chicks receiving high levels of such protein.

J Infect Dis, 1980 Aug, 142(2), 209 - 19
Transferrin-dependent growth inhibition of yeast-phase Histoplasma capsulatum by human serum and lymph; Sutcliffe MC et al.; Nonspecific host defense mechanisms that may limit growth of yeast-phase Histoplasma capsulatum in vivo were examined using an in vitro system of cell-free liquid culture . Native human transferrin in serum and lymph, or purified transferrin added to serum-free medium, inhibited yeast replication 10- to 50-fold . Supplementation of serum with iron to complete or almost complete saturation of total iron-binding capacity neutralized inhibition . Substitution of Zn++, Mn++, or Cu++ for Fe++ did not affect inhibition . Neither complement nor antibody was a relevant factor . Results of culture in medium with unsaturated transferrin followed by replenishment with iron indicated that iron deprivation was either fungistatic or fungicidal, depending on the yeast strain and, in serum-free medium, on the iron content of transferrin . Transferrin-dependent fungistasis was associated with morphologic alteration of yeasts as determined by electron microscopy . Thus, susceptibility of yeast-phase H . capsulatum to iron starvation by unsaturated transferrin may contribute to their low virulence in vivo.

Biokhimiia, 1980 Aug, 45(8), 1433 - 41
{Cause of the appearance of cyanide-resistant respiration in the yeast Candida lipolytica}; Akimenko VK et al.; Changes in the activity of the cell respiration of the yeast Candida lipolytica and its ATP, ADP, NADH, NAD+ pools during the development of the cyanide-resistant respiration were studied . A change-over of the yeast culture to the stationary growth phase conditioned by glucose exhaustion or aerobic incubation of the resting cells in the exponential growth phase without the exogenous carbon source were shown to be accompanied by: 1) decrease of the rate of oxygen consumption; 2) appearance of the cyanide-resistant respiration; 3) appearance of the benzhydroxamic acid-sensitive respiration; 4) appearance of stimulating dinitrophenol action on the rate of oxygen consumption; 5) increase in the ATP content and decrease of the ADP content in the cells . It was concluded that the appearance of the cyanide-resistant respiration is induced by the decrease of the activity of the respiratory chain due to the increase of the ATP concentration and the decrease of the ADP concentration in yeast cells . The functioning of the cyanide-resistant pathway of the electron transfer is one of the ways of NAD+ pool regulation in yeast cells.

Genetics, 1980 Aug, 95(4), 891 - 903
Assembly of the mitochondrial membrane system: nuclear suppression of a cytochrome b mutation in yeast mitochondrial DNA; Coruzzi G et al.; In a previous study, a mitochondrial mutant expressing a specific enzymatic deficiency in co-enzyme QH2-cytochrome c reductase was described (TZAGO-LOFF, FOURY and AKAI 1976) . Analysis of the mitochondrially translated proteins revealed the absence in the mutant of the mitochondrial product corresponding to cytochrome b and the presence of a new low molecular weight product . The premature chain-termination mutant was used to obtain suppressor mutants with wild-type properties . One such revertant strain was analyzed genetically and biochemically . The revertant was determined to have a second mutation in a nuclear gene that is capable of partially suppressing the original mitochondrial cytochrome b mutation . Genetic data indicate that the nuclear mutation is recessive and is probably in a gene coding for a protein involved in the mitochondrial translation machinery.

Proc Natl Acad Sci U S A, 1980 Aug, 77(8), 4504 - 8
In vitro synthesis of repressible yeast acid phosphatase: identification of multiple mRNAs and products; Bostian KA et al.; Antibodies to repressible nonspecific acid phosphatase {APase; orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2} purified from Saccharomyces cerevisiae were used to detect the in vitro products of APase mRNA . Immunoprecipitation of cell-free synthesized protein and of in vivo enzyme from cell extracts has shown that derepression of enzyme synthesis in situ is the result of de novo appearance of functional mRNA followed by de novo protein synthesis . At least three unique APase polypeptides are synthesized in vitro from separate mRNAs and appear to be glycosylated in vivo to form secreted enzyme.

Eur J Biochem, 1980 Aug, 109(2), 417 - 24
Characterization of the flavoenzyme enoyl reductase of fatty acid synthetase from yeast; Fox JL et al.; Enoyl reductase in the fatty acid synthetase from brewer's yeast, a flavoenzyme function, has been used as a specific probe for one partial activity of the multi-functional enzyme . The enzyme has an absorption maximum at 460 nm with epsilon = 18600 M-1 cm-1 and A280 = 1.37 mg-1 ml . The circular dichroism spectrum shows negative peaks at 373 and 466 nm . The fluorescence maximum is at 540 nm . The apoenzyme has an absorption maximum at 279 nm and shows fluorescence at 345 nm . The association constant for the FMN is 4 X 10(7) M-1 . The redox potential was determined as Eh = --0.193 V . The reductase is characterized as a 'true' transhydrogenase as no flavin free radical can be obtained by photochemical or chemical reduction or oxidation, i.e . it only functions via two-electron steps . An interpretation of the hydrophobic nature of the flavin binding site based on spectral data is presented.

Eur J Biochem, 1980 Aug, 109(1), 51 - 9
The ligand specificity of the (adenosine 3',5'-monophosphate)-binding site of yeast glyceraldehyde-3-phosphate dehydrogenase . Interaction with adenosine derivatives and pharmacologically-active compounds; Brownlee AG et al.; The high-affinity cAMP-binding site of form-II yeast glyceraldehyde-3-phosphate dehydrogenase has a marked specificity for adenosine derivatives, such ligands including N6-substituted adenosine derivatives active as cytokinins n plant systems and adenine nucleotides . Of a wide range of nucleotides and nucleosides examined only adenosine derivatives bind to the cAMP binding site . A variety of antimitotic compounds (including colchicine, colcemid and phenylcarbamate derivatives), adrenergic receptor antagonists (alprenolol and propranolol) and non-steroidal anti-inflammatory agents (notably indomethacin and flufenamic acid) displace cAMP from glyceraldehyde-3-phosphate dehydrogenase . Colchicine, colcemid, N6-furfuryladenosine, indomethacin, flufenamic acid and propranolol inhibit cAMP binding to the enzyme in an apparently competitive fashion . Given the evolutionary conservatism and abundance of glyceraldehyde-3-phosphate dehydrogenase, the affinity of the cAMP-binding site of this enzyme for a variety of structurally-disparate pharmacologically-active compounds compromises simple one-site interpretations of physiological responses to these agents.

Cell, 1980 Aug, 21(1), 217 - 26
Plasmids controlled exclusion of the K2 killer double-stranded RNA plasmid of yeast; Wickner RB; Saccharomyces strains of two types (K1+R1+ and K2+R2+) kill each other and K-R--sensitive strains by secreting protein toxins . K1 killer strains carry a 1.25 X 10(6) dalton double-stranded RNA plasmid, {KIL-k1}, while K2 killers have a 1.0 X 10(6) dalton double-stranded RNA plasmid, {KIL-k2} . Mating {KIL-k1} haploids with {KIL-k2} haploids yields only {KIL-k1} diploids, that is, {KIL-k1} excludes {KIL-k2} . {EXL}, a new non-Mendelian genetic element from a nonkiller strain, excludes {KIL-k2} but does not exclude {KIL-k1} . A second new non-Mendelian genetic element, called {NEX}, when present prevents {EXL} from excluding {KIL-k2} . {NEX} does not prevent {KIL-k1} or {KIL-s1} (a suppressive mutant of {KIL-k1}) from excluding {KIL-k2} . A chromosomal gene, called MKT1, is needed for maintenance of {KIL-k2} if {NEX} is present . In the absence of {NEX}, {KIL-k2} does not need MKT1 . {KIL-k1} does not need MKT1 even if {NEX} is present . {EXL} replication depends on at least the products of MAK1, MAK3, MAK10 and PET18 . {NEX} replication depends on MAK3 but is independent of MAK4, MAK6, MAK27 and MKT1.

Cell, 1980 Aug, 21(1), 205 - 15
Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway; Novick P et al.; Cells of a Saccharomyces cerevisiae mutant that is temperature-sensitive for secretion and cell surface growth become dense during incubation at the non-permissive temperature (37 degrees C) . This property allows the selection of additional secretory mutants by sedimentation of mutagenized cells on a Ludox density gradient . Colonies derived from dense cells are screened for conditional growth and secretion of invertase and acid phosphatase . The sec mutant strains that accumulate an abnormally large intracellular pool of invertase at 37 degrees C (188 mutant clones) fall into 23 complementation groups, and the distribution of mutant alleles suggests that more complementation groups could be found . Bud emergence and incorporation of a plasma membrane sulfate permease activity stop quickly after a shift to 37 degrees C . Many of the mutants are thermoreversible; upon return to the permissive temperature (25 degrees C) the accumulated invertase is secreted . Electron microscopy of sec mutant cells reveals, with one exception, the temperature-dependent accumulation of membrane-enclosed secretory organelles . We suggest that these structures represent intermediates in a pathway in which secretion and plasma membrane assembly are colinear.

Clin Chem, 1980 Aug, 26(9), 1278 - 80
Kinetic ethylene glycol assay with use of yeast alcohol dehydrogenase; Eckfeldt JH et al.; We describe a rapid, accurate, and precise two-point kinetic assay for ethylene glycol . The method involves use of a standard kit for ethanol determination with yeast alcohol dehydrogenase, and of a centrifugal analyzer . Alcohol dehydrogenase catalyzes the oxidation of ethylene glycol in a trichloroacetic acid-precipitated specimen; the resulting NADH production is monitored at 340 nm . The reaction rate is linear with concentration to 1.5 g of ethylene glycol per liter . Interference from methanol, ethanol, and isopropanol was easily recognized after a 30-min incubation at 100 degrees C . We believe that the method can be readily adaptable to any narrow-bandwidth, stable, temperature-controlled spectrophotometer and so should provide more widely for the prompt assessment of patients in whom ethylene glycol poisoning is suspected.

Parazitologiia, 1980 Aug, 14(4), 354 - 7
{Removal of accompanying yeast fungi from cultures of trichomonad strains (Polymastigina)}; Ryigas EM et al.; For purifying the cultures of Trichomonas vaginalis and T . hominis from associating yeasts we inoculated them into the upper layer of a viscous medium containing 0.1% agar (Teras, 1955; Tompel, Teras, 1976) poured into a burette . On the 2nd or 3rd day after inoculating the first drops obtained from the lower end of the burette contained as a rule only trichomonads . For purifying the cultures of T . tenax from associating yeasts we prepared a special semisolid medium from the liquid egg medium (Wantland e . a., 1963) by adding agar (0.5%), levorine (50--600 units/1 ccm) and some pieces of solid egg medium (Hallmann, 1953) . The curve of an U-tube was filled with this medium and into both branches pure liquid egg medium was poured . In a few days after inoculating the culture of T . tenax with yeasts into one branch of the tube we obtained from the other branch of the tube trichomonads without yeasts.

J Inorg Biochem, 1980 Aug, 13(1), 11 - 21
Chromium in biological systems, I . Some observations on glucose tolerance factor in yeast; Mirsky N et al.; Glucose tolerance factor (GTF) has been isolated from a commercially available yeast extract powder, by a simple procedure under mild conditions . This cationic yellow material enhances considerably CO2 production in several yeast strains, after a lag time which can be eliminated by preincubation with glucose . The enhancement of CO2 production by GTF is not specific for glucose, and its effect on galactose raises the possibility that it influences the transport of the sugar to the cells . The ineffectiveness of GTF on cell free extract and the results of a Michaelis plot for CO2 production support this hypothesis.

Eur J Biochem, 1980 Aug, 109(1), 61 - 6
Turnover of yeast fructose-bisphosphatase in different metabolic conditions; Funayama S et al.; Earlier work demonstrated that addition of glucose to yeast growing on noncarbohydrate carbon sources sharply reduces the levels of fructose bisphosphatase . This report indicates that the decrease in the levels of fructose bisphosphatase is accompanied by a parallel decrease of cross-reacting material to specific antibody to fructose bisphosphatase . Use of the specific antibody shows that the loss of activity is irreversible and that its reapperance requires synthesis of protein de novo . The protein is highly stable during growth in ethanol (half life about 90 h) . Addition of glucose increases the rate of degradation abut 200-fold . It is shown that the values of the rates of synthesis and degradation of fructose bisphosphatase vary with the metabolic situation of the yeast.

Cell, 1980 Aug, 21(1), 239 - 49
DNA rearrangements associated with a transposable element in yeast; Roeder GS et al.; The his4-912 mutation results from insertion of a 6200 bp transposable element into the his4 gene of yeast . In order to clone the his4-912 mutation, the plasmid pBR322 was integrated into the his4 gene by means of yeast transformation, and then the vector sequences and the his4-912 insertion element were excised as a single restriction fragment . This his 4-912 insertion element is homologous to Ty1, a family of repetitive yeast DNA sequences . His+ revertants derived from the his4-912 mutant carry a number of chromosomal aberrations including deletions, translocations, a transposition and an inversion . The majority of His+ revertants result from deletions which have both endpoints within the element and which leave behind only 300 bp of the insertion element . Other derivatives of the his4-912 mutant carry deletions which have one endpoint in the insertion element and one endpoint in the his4 coding sequence . In two His+ revertants carrying reciprocal translocations, the chromosome III translocation breakpoints occur within the his4-912 insertion element . A His+ revertant carrying an inversion of most of the left arm of chromosome III may be an intermediate in transposition of the his4-912 insertion element to a new site on chromosome III.

Cell, 1980 Aug, 21(1), 227 - 37
Genetic events associated with an insertion mutation in yeast; Chaleff DT et al.; The his4-912 mutation shares similar genetic properties with mutations promoted by procaryotic insertion elements . This mutation lacks all three his4 functions . Many different classes of His+ revertants have been obtained from his4-912 . The most frequent class of His+ revertants results from a site mutation which confers a cold-sensitive His- phenotype . Other classes of revertants contain translocations (one between chromosomes I and III and the other between chromosomes III and XII), a transposition of the his4 region to chromosome VIII, and an inversion of most of the left arm of chromosome III . Another class contains deletions which extend from his4-912 into the his4 region . In each of these classes of revertants, the his4 region is closely linked to the chromosomal aberration . Many of these revertants contain additional changes in chromosome structure (duplication, deletion and aneuploidy) that are unrelated to the reversion of his4-912 to His4+.

Eur J Biochem, 1980 Aug, 109(2), 589 - 601
Biosynthesis of the core region of yeast mannoproteins . Formation of a glucosylated dolichol-bound oligosaccharide precursor, its transfer to protein and subsequent modification; Lehle L; A new membrane preparation from Saccharomyces cerevisiae was developed, which effectively catalyzes the synthesis of large oligosaccharide-lipids from GDP-Man and UDP-Glc allowing a detailed study of their formation and size . The oligosaccharide from an incubation with GDP-Man could be separated by gel filtration chromatography into several species consisting of two N-acetylglucosamine (GlcNAc) residues at the reducing end and differing by one mannos unit; the major compound formed has the composition (Man)9(GlcNAc)2 . Upon incubation with UDP-Glc, three oligosaccharides corresponding to the size of (Glc)1-3(Man)9(GlcNAc)2 are formed . Thus, the oligosaccharides generated in vitro by the yeast membranes appear to be identical in size with the oligosaccharides found in animal systems . In addition the results indicate that dolichyl phosphate mannoe (DolP-Man) is the immediate donor in assembling the oligosaccharide moiety from (Man)5(GlcNAc)2 to (Man)9(GlcNAc)2 . All three glucose residues are transferred from DolP-Glc . Experiments with isolated {Glc-14C}oligosaccharide-lipid as substrate demonstrated that the oligosaccharide chain is transferred to an endogenous membrane protein acceptor . Moreover, transfer is followed by an enzymic removal of glucose residues, due to a glucosidase activity associated with the membranes . Glucose release from the free {Glc-14C}oligosaccharide is less effective than from protein-bound oligosaccharide . Glycosylation was also observed using {Man-14C}oligosaccharide-lipid or DolPP-(GlcNAc)2 as donor . However, transfer in the presence of glucose seems to be more rapid . The mannose-containing oligosaccharide, released from the lipid, was shown to function as a substrate for further chain elongation reactions utilizing GDP-Man but not DolPP-Man as donor . It is suggested that the immediate precursor in the synthesis of the heterogeneous core region, (Man)12-17(GlcNAc)2, of yeast mannoproteins is a glucose-containing lipid-oligosaccharide with the composition (Glc)3(Man)9(GlcNAc)2, i.e . only part of what has been defined as inner core is built up on the lipid carrier . After transfer to protein the oligosaccharide is modified by excision of the glucose residues, followed subsequently by further elongation from GDP-Man to give the size of th oligosaccharide chains found in native mannoproteins.

Mol Biol Rep, 1980 Jul 31, 6(2), 83 - 7
A rapid method for mapping exposed cytosines in polyribonucleotides . Application to tRNATrp (yeast, beef liver); Mashkova TD et al.; A rapid method for mapping exposed cytosine residues in 5'-{32P}-labeled RNA molecules is suggested . The exposed cytosines (C's) are converted into uracyls (U's) by bisulphite treatment at pH 5.8 in the presence of Mg2+, followed by complete modification of the residual (non-exposed) C's by a methoxyamine and bisulphite mixture at pH 5.0 . The control RNA is modified only by methoxyamine and bisulphite without the preliminary C leads to U conversion . The location of the exposed C's is determined by comparing the products of partial T1, T2, A and U2 ribonuclease digestions of the C leads to U converted and control RNAs after slab gel polyacrylamide electrophoresis and autoradiography . The method has been applied for mapping exposed cytosine bases in tRNATrp (yeast) which have been found in the anti-codon loop and at the 3'-end of the molecule . In tRNATrp (beef liver), in addition to the same exposed bases, C in the diHU-loop is exposed . The data obtained are in full agreement with what is known about exposed C's for other tRNAs.

J Biol Chem, 1980 Jul 25, 255(14), 6653 - 61
Yeast mutant defective in phosphatidylserine synthesis; Atkinson K et al.; Phospholipid biosynthesis in a mutant of Saccharomyces cerevisiae (cho1) which lacks phosphatidylserine (Atkinson, K . D., Jensen, B., Storm, E., Kolat, A . I., Henry, S . A . & Fogel, S . (1980) J . Bacteriol . 141, 558-564) has been examined . The ability of cells of this strain to synthesize phosphatidylserine in vitro in a cell-free system is reduced at least 10-fold, whereas other phospholipid-synthesizing activities are present at normal or slightly elevated levels . While all phospholipid biosynthetic activities, except phosphatidylserine synthesis, can be demonstrated in vitro in the cho1 mutant, the entire pattern of phospholipid synthesis, accumulation, and turnover in vivo is distorted . Phosphatidylinositol synthesis is elevated, as is phosphatidylcholine synthesis . In addition, the turnover of phosphatidylcholine is more rapid in the cho1 mutant . The cho1 mutant appears to use almost exclusively the alternative pathway described by Kennedy and Weiss (1956) J . Biol . Chem . 222, 193-214) for the production of phosphatidylethanolamine and phosphatidylcholine, bypassing phosphatidylserine as an intermediate.

Nucleic Acids Res, 1980 Jul 11, 8(13), 2985 - 97
Yeast viral RNA polymerase is a transcriptase; Bruenn J et al.; ScV-L is a simple double-stranded RNA virus of yeast, consisting of a 4.8 kilobase pair double-stranded RNA (L) encapsidated in isometric particles composed mainly of one polypeptide (ScV-Pl) of 88,000 daltons . L encodes ScV-Pl . There is a capsid-associated RNA polymerase that synthesizes in vitro predominantly single-stranded RNA . We show that this polymerase activity is a transcriptase, at the least one product of which is the mRNA for ScV-Pl . The transcript, like its template, is uncapped.

J Biol Chem, 1980 Jul 10, 255(13), 6450 - 5
A mutation of the B220 subunit gene affects the structural and functional properties of yeast RNA polymerase B in vitro; Ruet A et al.; The Saccharomyces cerevisiae mutant rpo B1 produces a DNA-dependent RNA polymerase B defective in RNA synthesis in vitro . RNA polymerase B purified from the mutant is altered both structurally and functionally . The enzyme is defective in the RNA chain initiation and elongation reactions . Enzyme-DNA binding is comparatively much less affected . These enzymological defects in the mutant enzyme are enhanced at elevated ionic strengths . Purified rpo B1 RNA polymerase B is lacking B32 and B16.5 subunits . However, the low activity of the mutant enzyme cannot be accounted for only by the loss of these two polypeptides . Wild type enzyme devoid of B32 and B16.5 subunits can be obtained after a mild urea treatment . This enzyme variant, called RNA polymerase B, does not share the enzymological properties of the mutant RNA polymerase . Immunoprecipitation of the enzyme from crude extracts shows that, in the rpo B1 mutant, a normal amount of RNA polymerase B is synthesized which contains the full complement of subunits . The polypeptide chain altered by the rpo B1 mutation was identified by partial proteolysis with proteinase K in the presence of sodium dodecyl sulfate . The 35S-labeled peptide pattern generated from the B220 subunit of the mutant enzyme differs markedly from the peptide pattern of the wild type subunit . The rpo B1 mutation therefore alters the B220 subunit, suggesting a role for this subunit in RNA chain elongation and in the association of the B32 and B16.5 subunits to the RNA polymerase molecule.

Biochim Biophys Acta, 1980 Jul 10, 614(1), 121 - 33
Partial purification, characterization and localization of the membrane-associated invertase of yeast; Babczinski P; The membrane-associated isozyme of invertase (beta-D-fructofuranoside fructo-hydrolase, EC 3.2.1.26) -- precursor of the external glycoprotein invertase (Babczinski, P . and Tanner, W . (1978) Biochim . Biophys . Acta 538, 426-434) - has been purified 60-fold from deoxycholate extracts of derepressed yeast cells . The partially purified enzyme exhibits considerable stability as a salt-free lyophilized powder . Its molecular weight, in this precursor form, has been determined by by sodium dodecyl sulphate (SDS) gel electrophoresis to be 180 000 daltons . This correlates well with the presence of only the inner core carbohydrate parts of the external invertase . The enzyme can be split completely by treatment with endo-beta-N-acetyl-glucosaminidase H from Streptomyces griseus, demonstrating the presence of a di-N-acetylchitobiosyl-asparagine linkage . The proteinaceous split product is still active and has a molecular weight of approx . 120 000 . The enzyme cannot be transferred into a supernatant fraction upon osmotic shock treatment of yeast membrane vesicles, indicating that it is strictly membrane-bound . After separation of yeast membranes on a sucrose density gradient, precursor invertase is predominantly associated with two gradient membrane fractions which most probably represent rough and smooth endoplasmic reticulum.

J Biol Chem, 1980 Jul 10, 255(13), 6173 - 80
Assembly of the mitochondrial membrane system . Sequence of the oxi 2 gene of yeast mitochondrial DNA; Thalenfeld BE et al.; The region of mitochondrial DNA (mtDNA) containing the oxi 2 locus has been sequenced in a rho- clone (DS40) derived from the respiratory competent strain D273-10B/A48 of Saccharomyces cerevisiae . The DS40 clone was established to have retained only genetic markers in the oxi 2 locus and to have a segment of mtDNA extending from 18.6 to 24.3 units of the wild type map . The mitochondrial genome of DS40 includes a sequence that has been tentatively identified as the structural gene of Subunit 3 of cytochrome oxidase . The coding sequence is 810 nucleotides long and generates a protein with a molecular weight of 30,340 . The amino acid composition of the oxi 2 gene product deduced from the nucleotide sequence is in agreement with the composition of the purified Subunit 3 of yeast cytochrome oxidase . The orientation of the DS40 mtDNA segment relative to wild type mtDNA indicates that the oxi 2 gene is transcribed from the same DNA strand as the oxi 1 and several other mitochondrial genes.

Biochemistry, 1980 Jul 8, 19(14), 3131 - 7
Interaction of metal(III)-adenosine 5'-triphosphate complexes with yeast hexokinase; Viola RE et al.; In the presence of glucose, yeast hexokinase is specifically and strongly inhibited by all MIIIATP (M = metal) complexes that do not hydrolyze at neutral pH, as long as the ionic radius of the metal is less than 0.89 A . Ki values vary from the micromolar range (0.16 microM for AlATP at pH 7, for example) to as low as 13 nM for LuATP . With glucose and fructose, the tightly bound complexes also show reversible, slow binding behavior, but with poor substrates, little or no change in inhibition constant with time is observed . The kinetics of citrate as an activator of the hexokinase reaction are consistent with its reaction with AlATP present as a contaminant in commercial ATP to form Al citrate . The complex of Al(III) with citrate is 5 orders of magnitude more stable than AlATP, whose Kd is 0.7 microM at pH 7 . ATP that has been treated with excess EDTA and adsorbed on and eluted from charcoal is free of aluminum, and citrate no longer affects the kinetics of the hexokinase reaction . Glycerokinase is also specifically inhibited by trivalent metal ATP complexes (Ki = 4 microM at pH 7 for AlATP).

Poult Sci, 1980 Jul, 59(7), 1471 - 9
The use of methanol-grown yeast LI-70 in feeds for broilers; Succi G et al.; In 60-day feeding trials, broilers were fed commercial diets in which different amounts of methanol-grown yeast LI-70 replaced fish and soybean meal . In the first trial, all-mash diets containing up to 15% yeast produced growth rates and efficiencies of feed conversion almost equal to those of the soybean meal control and slightly below those of the fish meal control . In the second trial, pelleted diets containing up to 25% yeast were used . For yeast levels up to 15%, growth rates were faster than for the soybean meal control and slightly slower than for the fish meal control . Diets with more than 15% yeast lacked selenium . Diets containing 25% yeast as the sole source of protein but supplemented with .3 ppm selenium produced growth rates and efficiencies of feed conversion equal to those of the controls.

Can J Biochem, 1980 Jul, 58(7), 565 - 72
Yeast cell wall, membrane, and soluble marker polypeptides identified by comparative two-dimensional electrophoresis; Robertson AJ et al.; Yeast cell wall, plasma membrane, total spheroplast, and total soluble protein fractions were isolated from exponentially growing Saccharomyces cerevisiae batch cultures . The cell wall, plasma membrane, and soluble protein fractions were obtained by mechanical disruption of intact yeast cells under identical osmotic conditions . Electron micrographs of purified wall fractions appeared free of vesicular membrane contamination and micrographs of plasma membrane vesicles were free of cell wall contamination . Various stages of cell wall purification were monitored by electron microscopy and comparative two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis . This resulted in the identification of a glycopeptide designated 16w in the cell wall fraction, with an apparent isoelectric point of 5.0 and an apparent molecular weight of 25 000 . Protein analyses of soluble and plasma membrane protein fractions failed to detect component 16w . Two-dimensional protein analyses of total cellular homogenates were capable of resolving the cell wall glycopeptide 16w . However, protein separations of spheroplasts formed by glusulase degradation of the cell wall complex did not detect 16w . These observations suggest that component 16w is unique to the cell wall fraction . In addition, comparison of two-dimensional gels of soluble and plasma membrane proteins, with a total cellular homogenate, tentatively identified several polypeptides unique to each of the soluble and plasma membrane fractions.

Genetics, 1980 Jul, 95(3), 631 - 48
Interconversion of yeast cell types by transposable genes; Klar AJ; The a and alpha cell types of budding yeast saccharomyces cerevisiae are controlled by alternate alleles of the mating-type locus (MAT), MATa and mat alpha . The cell types can be interconverted by switching alleles of MAT . The loci HMRa and HML alpha, which are loosely linked to MAT, are involved in mating-type switching . Experimental evidence for their role in MAT interconversion is presented . As a result of switching, the homothallic and heterothallic strains containing the amber and ochre mutations within the HMRa locus yield corresponding amber and ochre mutant mata loci . Similarly, the hml alpha mutant strain generates mat alpha mutant alleles . That is, specific mutations from HMRa and HML alpha are transmitted to MAT . A replica of the mating-type coding information originating from these loci is transposed to MAT, where it replaces the existing information . Furthermore, "Hawthorne deletions" in strains containing hmra-amber/ochre result in production of mata-amber/ochre alleles . Therefore, genetic information for MATa resides at HMRa . The switches occur in a defined set of clonally related cells . Thus, the efficient interconversion of yeast cell types is mediated by an unidirectional transfer of genetic information between nonallelic sites in a nonrandom and programmed fashion . The results are inconsistent with the "flip-flop" models, but satisfy a key prediction of the general controlling element and the specific cassette models proposed for mating-type interchange.

Genetics, 1980 Jul, 95(3), 589 - 609
Reversion from suppression to nonsuppression in SUQ5 {psi+} strains of yeast: the classificaion of mutations; Cox BS et al.; Reversion from the suppressed to nonsuppressed phenotype in strains of geno;type SUQ5 {psi+} ade2-1 his5-2 lys1-1 can1-100 ura3-1 has been induced by treatment with ethyl methanesulphonate, nitrosoguanidine or UV (254 nm) light . Spontaneously occurring revertants have also been selected by two different methods . Reversion has been shown to occur through a variety of nuclear mutations and through mutation of {psi+} to {psi-} . Nuclear mutations included back-mutation of SUQ5, antisuppressor mutations that were recessive, semi-dominant or dominant, and dominant or recessive mutations of genes required for the maintenance of the {psi+} factor . Complementation tests by which the various kinds of mutations could be distinguished from one another were designed . The spectra of spontaneously occurring and induced mutations have been described.

Thorax, 1980 Jul, 35(7), 523 - 5
Defective yeast opsonisation of serum in tuberculosis; Johnson NM et al.; We have studied the opsonising ability of the sera of 92 patients with tuberculosis . Fourteen per cent of these patients showed defective opsonising ability compared with 4% in a clinic control group . This increased frequency in TB was accounted for by the greatly increased proportion with defects found in patients with intrathoracic TB (21%) . We may have identified a section of the population with a specific genetically linked abnormality of a host defence mechanism which renders them more susceptible to intrathoracic TB . Further population studies are required.

Proc Natl Acad Sci U S A, 1980 Jul, 77(7), 3942 - 6
Replicator regions of the yeast mitochondrial DNA responsible for suppressiveness; Blanc H et al.; Hypersuppressiveness is a heritable property of some rho- mutants (called HS) that, in crosses to rho+, give rise to about 100% rho- cells . The mtDNAs of all HS rho- mutants reveal a common organization: they all share a homologous region of about 300 base pairs (called rep) and the fragments retained are always short (ca . 1% of the wild-type genome) and tandemly repeated . Using one HS rho- mutant as an example, we show that, after crosses with rho+ strains, the mitochondrial genome of the progeny is indistinguishable from that of the HS parent . This suggests that HS mtDNA molecules have a decisive selective advantage for replication during the transient heteroplasmic stage that follows zygote formation, the rep regions playing a role in the control of replication initiation of the mtDNA molecules . The complete nucleotide sequence of one HS rho- mutant and its localization in the oli1-rib3 segment of the rho+ mitochondrial genome are presented . Comparison of the nucleotide sequences of the rep regions of two different HS rho- mutants reveals that several rep sequences must exist in the wild-type genome, probably as a result of duplications of an originally unique ancestor.

Cell, 1980 Jul, 20(3), 701 - 9
Mutations at the yeast SUP4 tRNATyr locus: DNA sequence changes in mutants lacking suppressor activity; Kurjan J et al.; Yeast strains harboring indepjendent mutations within the SUP4 tyrosine tRNA gene have been selected by virtue of their inactivating effect upon the SUP4-o UAA suppressor . Three fourths of the mutations at SUP4 are point alterations; the rest resemble the deletions described by Rothstein (1979) . A meiotic genetic fine structure map of the locus was made by crossing 69 of the mutants in all combinations and testing for the frequency of SUP4-o recombinants . The sequences of SUP4 genes cloned from 32 mutant strains were determined by the dideoxynucleotide terminator method, using as primer a synthetic oligodeoxynucleotide corresponding to a sequence adjoining the SUP4 3' terminus . The positions of the DNA sequence alterations showed good colinearity with the positions of the mutations on the genetic map . One of the 26 mutant sites found by DNA sequencing lies within the intervening sequence . At this site three repeat mutations were found, each changing AT leads to TA . Whereas mutations were generally rather uniformly distributed throughout the tRNATyr coding sequence, none occurred in the DNA sequences flanking the mature tRNATyr sequence or in a 12 nucleotide sequence including the 10 bp which constitute the 3' side of the intervening sequence.

Mikrobiologiia, 1980 Jul-Aug, 49(4), 571 - 7
{Cytochrome P-450 content in yeast cells during growth on hexadecane}; Mauersberger S et al.; The content of cytochrome P-450 was studied in the cells of alkane oxidizing yeasts Candida guilliermondii, C . tropicalis and C . lipolytica . The cells of all the studied yeast strains growing on hexadecane were found to contain cytochrome P-450 . The cytochrome was not detected when the yeast strains grew on glucose . The concentration of cytochrome P-450 remained constant at the exponential growth phase, but decreased at the beginning of the stationary growth phase . Cytochrome P-450 was shown to be synthesized de novo in the course of physiological adaptation of the cells to hexadecane.

J Inorg Biochem, 1980 Jul, 12(4), 323 - 34
Binding of inhibitory metals to yeast enolase; Elliott JI et al.; Certain divalent cations can inhibit yeast enolase by binding at sites that are distinct from those metal binding sites normally associated with catalytic activity, i.e., the conformational and catalytic binding sites . By using a buffer that does not compete with metal ions (tetrapropylammonium borate) Zn, Co, Mn, Cu, Cd, and Ni are found to exhibit similar inhibitory characteristics . Inhibition by those metals is alleviated by the addition of imidazole or tris buffer and, for zinc, by a metal chelating agent (Calcein) . Inhibition by zinc was examined in detail through binding studies and enzymatic activity measurement . In tetrapropylammonium buffers at pH 8.0, enolase binds up to four moles of zinc per mole of enzyme (two moles per subunit) . An imidazole concentration of 0.05 M reduces the binding: in the absence of substrate, just two moles of zine per enzyme are bound . The enzyme will bind two additional moles of zinc upon the addition of substrate in either buffer, but the enzyme in tetrapropylammonium buffer is nearly inactive . Inhibition is, therefore, correlated with the binding of two moles of zinc per mole of enzyme . Some additional metal ions, Ca, Tb, Hg, and Ag also caused inhibition of yeast enolase but not by binding to the inhibitory site described.

J Biochem (Tokyo), 1980 Jul, 88(1), 247 - 54
Biosynthesis of ergosterol in cell-free system of yeast; Nishino T et al.; We previously proposed the occurrence of multiple pathways in the ergosterol biosynthesis of yeast, based on the results of examination of 14C-incorporation into sterols from L-{methyl-14C}methionine which was given to the intact cells of yeast . This led us to investigate the validity of the pathways by experiments with the cell-free system . Highly active cell-free extracts could be prepared by disruption of yeast cells with a Vibrogen Cell Mill in the presence of 0.1 mM dithiothreitol . This preparation catalyzed 14C-incorporation from {14C}methionine into ergosterol with a high yield . This preparation was found to be favorable for elucidation of ergosterol synthesis, since only a small amount of radioactivity was incorporated into fatty acid ester form of sterols which were reported to be inactive as a substrate for sterol synthesis reaction . Time course experiment of 14C-incorporation from {14C}methionine into various sterols under aerobic conditions showed that ergosta-8,24(28)-dien-3 beta-ol was a precursor for ergosta-7,24(28)-dien-3 beta-ol and that radioactivities were converted through ergosta-5,7,24(28)-trien-3 beta-ol and ergosta-5,7,22,24(28)-tetraen-3 beta-ol into ergosterol with time . In contrast, similar experiments under anaerobic conditions showed that ergosta-7,24(28)-dien-3 beta-ol accumulated and very little conversion of radioactivity into ergosterol occurred . In addition, the results indicated that oxygen was required for the introduction of double bond into 22 position as well as into 5 position . The results obtained with the cell-free system supported the validity of the proposal of multiple pathways of ergosterol synthesis in the intact cells.

J Biochem (Tokyo), 1980 Jul, 88(1), 151 - 8
Folding of yeast 5S ribosomal RNA induced by magnesium binding; Maruyama S et al.; The magnesium-induced conformational changes of yeast 5S ribosomal RNA have been studied by means of difference absorption spectroscopy and circular dichroism . A hypochromic difference absorption spectrum with a trough at approximately 260 nm was observed together with a slight increase and blue shift of the peak at 265 nm and a significant increase of the absolute magnitude of the trough at 208 nm in the circular dichroism spectrum . The magnesium concentration dependence of the difference absorption gave a Hill coefficient of 2.0 +/- 0.2 . All of the equilibrium data indicate that magnesium ions produce a more ordered form of the molecule . Transient kinetic studies using a magnesium concentration-jump were carried out . The kinetic curves were biphasic, each phase being associated with a relatively slow unimolecular conformational change induced by magnesium binding . A simple scheme was able to accommodate all of the equilibrium and kinetic data, and the kinetic parameters were calculated . Activation parameters for the unimolecular steps suggest that the conformational changes of the 5S RNA involved the breaking of several base pairs and tertiary folding.

J Bacteriol, 1980 Jul, 143(1), 463 - 70
Encapsidation of yeast killer double-stranded ribonucleic acids: dependence of M on L; Bostian KA et al.; Virus-like particles containing either L or M double-stranded ribonucleic acid (dsRNA) were isolated from a killer toxin-producing strains of Saccharomyces cerevisiae (K+ R+) . At least 95% of M- and 87% of L-dsRNA were recovered in virus-like particle-containing fractions . The major capsid polypeptides (ScV-P1) of both L and M virus-like particles were shown to be identical, and 95% of the cellular ScV-P1 was found in the virus-like particle-containing fractions . Since L-dsRNA encodes ScV-P1, provision of this protein for encapsidation of M-dsRNA defines at least one functional relationship between these dsRNA genomes and associates the L-dsRNA with the killer character . If encapsidation of M-dsRNA is essential for its replication or expression, then L-dsRNA plays an essential role in maintenance or expression of the killer phenotype . The relationship between the L- and M-dsRNA genomes would be analogous to that between a helper and a defective virus . The presence of only minor quantities or uncomplexed dsRNA and ScV-P1 suggests that their production is stringently coupled.

Proc Natl Acad Sci U S A, 1980 Jul, 77(7), 4160 - 4
The four cytoplasmically made subunits of yeast mitochondrial cytochrome c oxidase are synthesized individually and not as a polyprotein; Mihara K et al.; Subunit-specific antisera prepared against each of the four cytoplasmically made subunits (IV, V, VI, and VII) of yeast mitochondrial cytochrome c oxidase (EC 1.9.3.1) were used to precipitate immunoreactive polypeptides that were synthesized either in vitro, in a cell-free protein-synthesizing system programmed with total yeast mRNA, or in vivo, in intact cells and in spheroplasts, under conditions of pulse labeling, pulse-chase labeling, and continuous labeling . Using N-formyl-{35S}Met-rTNA as the only radioactively labeled component in the cell-free system, we demonstrated (i) that each of the four cytoplasmically made subunits is synthesized as a separate entity and not as part of a polyprotein as was claimed by others; (ii) that subunits IV, V, and VI are synthesized as precursors, larger by 1500-3000 daltons than their mature counterparts; in contrast, subunit VII is not synthesized as a larger precursor . Precursor forms of subunits IV, V, and VI identical to those synthesized in vitro were also detected in vivo by pulse-labeling of spheroplasts . The observed disappearance of these larger forms after a chase is compatible with the notion that they represent short-lived precursors that are rapidly converted to their mature counterparts during or shortly after import into mitochondria . Furthermore, using N-formyl-{35S}Met-tRNA, we provide definitive evidence that two of the cytoplasmically made subunits (beta and gamma) of another oligomeric inner mitochondrial membrane protein (F1-ATPase, EC 3.6.1.3) are not synthesized as part of a polyprotein but as individual precursors.

Proc Natl Acad Sci U S A, 1980 Jul, 77(7), 3998 - 4002
Cytoplasmically made subunits of yeast mitochondrial F1-ATPase and cytochrome c oxidase are synthesized as individual precursors, not as polyproteins; Lewin AS et al.; At least three subunits of yeast mitochondrial F1-ATPase (ATP phosphohydrolase, EC 3.6.1.3) and at least two subunits of cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) are synthesized outside the mitochondria and imported into the organelles as individual precursors that are between 2000 and 6000 daltons larger than the mature subunits . These precursors were shown to be primary translation products . Therefore, neither the five F1 subunits nor the four small cytochrome c oxidase subunits are synthesized as a single polyprotein.

J Biochem (Tokyo), 1980 Jul, 88(1), 97 - 102
Sterol-content lowering action of o-chlorobenzylchloride in yeast; Ariga N et al.; o-Chlorobenzylchloride, a simple aromatic halogen compound, was found to inhibit the growth of Saccharomyces cerevisiae and to lower the contents of sterols and fatty acids . The growth inhibition was considerably alleviated by the presence of sterols such as ergosterol and cholesterol and of unsaturated fatty acids such as oleate and linolenate . Inspection of effect of the inhibitor on the electron transport system related to the biosyntheses of these compounds revealed that the cytochrome contents and some enzyme activities in the system of the inhibited cells were much lower than those of the control cells . The features of the inhibition were similar to those of inhibition for other organisms by the hypocholesterolemic compounds such as triparanol and benzmalecene.

Nature, 1980 Jun 19, 285(5766), 579 - 81
Yeast mitochondrial tRNATrp can recognize the nonsense codon UGA; Martin NC et al.; DNA sequence analysis of mitochondrial genes that code for some mitochondrial proteins has suggested that the opal terminator, UGA, is used as a sense codon in mitochondria . The complete sequences of both the yeast and human genes coding for cytochrome oxidase subunit II contain UGA codons in the reading frame . When the protein sequences predicted by these DNA sequences are compared with the known protein sequence of bovine mitochondrial cytochrome oxidase subunit II, there are regions of homology, in which UGA codons correspond to tryptophan residues . Therefore it has been suggested that UGA specifies tryptophan in the mitochondrial code . We have isolated a yeast mitochondrial tRNATrp and used it to locate the mitochondrial tRNATrp gene in pBR322-mitochondrial DNA recombinants . DNA sequence analysis of this gene revealed that the mitochondrial tRNATrp anticodon is 5'UCA3' . Because there is a U in the wobble position, this tRNA can recognize and insert tryptophan into a growing polypeptide chain in response to the nonsense codon UGA.

Biochim Biophys Acta, 1980 Jun 13, 613(2), 482 - 7
alpha-Isopropylmalate synthase from yeast . A zinc metalloenzyme; Roeder PR et al.; Highly purified alpha-isopropylmalate synthase (3-hydroxy-4-methyl-3-carboxyvalerate 2-oxo-3-methylbutyrate-lysase (coA-acetylating), EC 4.1.3.12) from Saccharomyces cerevisiae is inactivated by various chelating agents . Atomic absorption spectrometry indicates that the enzyme contains approx . four gatoms of zinc per dimer of molecular weight of 130 000 . Dialysis against ethylenediaminetetraacetic acid at an initial concentration of 0.1 mM reduces the zinc content to about two gatoms of zinc per dimer . While such enzyme remains active, it has altered kinetic properties and is stimulated by Mn2+, in contrast to untreated enzyme . Dialysis against ethylenediaminetetraacetic acid at an initial concentration of 50 mM reduces the zinc content by more than 80% and causes almost complete loss of enzymatic activity . Activity can be restored by the addition of Zn2+, Mn2+, Fe2+, Co2+, or Cd2+.

J Biol Chem, 1980 Jun 10, 255(11), 5461 - 7
The yeast mitochondrial adenosine triphosphatase complex . Subunit stoichiometry and physical characterization; Todd RD et al.; Immunoprecipitation of uniformly labeled yeast submitochondrial preparations using a subunit-specific or a holoenzyme antiserum has been employed to determine the subunit stoichiometry of the oligomycin-sensitive ATPase complex . The Triton-solubilized enzyme consists of 10 types of subunits . The number of copies of each subunit, in order of decreasing molecular weight, is 3:3:1:2:1:2:2:1:2:3 . on the basis of the stoichiometry data, the ATPase complex has a molecular weight of 5.8 x 10(5) and contains a minimum of 20 polypeptide chains . Analysis of water-soluble ATPase (F1-ATPase) indicates that the stoichiometry of the three largest subunits of the enzyme is preserved in the absence of the other subunits . The molecular weights of both forms of the ATPase, derived from stoichiometry data, agree well with measurements obtained from gel filtration and sedimentation studies . The implications of these data for the structure, function, and assembly of the complex are discussed.

J Biol Chem, 1980 Jun 10, 255(11), 5320 - 8
Theoretical analysis of distribution of {18O}Pi species during exchange with water . Application to exchanges catalyzed by yeast inorganic pyrophosphatase; Hackney DD; A theoretical analysis has been derived which allows the analytical calculation of the complete distribution of 18O-labeled Pi species expected to occur during medium Pi equilibrium HOH exchange of {18O}Pi and to be produced by intermediate Pi equilibrium HOH exchange during net hydrolysis of {18O}PPi or other labeled phosphate compounds . The observed distributions with catalysis by yeast inorganic pyrophosphatase are found to agree closely with the theoretical values indicating that the exchange reaction can be adequately described by a unique value of the partitioning of bound Pi between release from the enzyme versus formation of bound PPi with loss of an oxygen to the water . The limitations on the exclusion of other mechanisms are discussed . The extent of this partitioning does change, however, under some experimental conditions . At low pH, with activation by Mg2+ or Mn2+, the relative rate of release of Pi is found to increase . The extent of exchange is also dependent on the nature of the activating metal, being greatest with Co2+ . During PPi hydrolysis with PPi in excess over Mg2+, a shift to lower extents of exchange is observed.

Biokhimiia, 1980 Jun, 45(6), 1068 - 74
{Control of the alternative pathway of electron transfer in mitochondria of the yeast Candida lipolytica}; Medentsev AG et al.; The dependence of the activity of the alternative cyanide-resistant electron transfer pathway in mitochondria of the yeast Candida lipolytica on the functional state of the main phosphorylating respiratory chain was studied . Oxidation of NAD-linked substrates both in active or uncoupled and controlled states by cyanide-resistant mitochondria was shown to be performed solely by the main respiratory chain . Succinate or alpha-glycerophosphate in the active or uncoupled state of the respiratory chain are oxidized solely by the main respiratory chain, whose changes in the controlled state are accompanied by activation of the alternative pathway of electron transfer . Exogenous NADH is oxidized both in active and controlled states of the respiratory chain by the main respiratory chain and the alternative pathway simultaneously . The transition of the respiratory chain from active to controlled state is followed therewith by an additional activation of the alternative pathway . It was concluded that the alternative pathway contribution to the total oxygen consumption by mitochondria is controlled by the activity of the main respiratory chain . The alternative pathway accomplishes the transfer of reducing equivalents excessive for the main respiratory chain.

Biokhimiia, 1980 Jun, 45(6), 1004 - 9
{Interactions of yeast hexokinase with ATP and AMP 4-(N-2-chloroethyl-N-methylamino)benzylamidates}; Buneva VN et al.; The interactions of ATP and AMP 4-(N-2-chloroethyl-N-methylamino)-benzylamidates with yeast hexokinase were studied . It was found that the ATP analog does not interact with hexokinase . The AMP analog irreversibly and almost completely inactivates hexokinse . A strong protective effect is exerted by MgATP . The value of apparent Ki for the AMP analog is equal to 2.10(4) M . The existence of affinity modification is postulated.

Proc Natl Acad Sci U S A, 1980 Jun, 77(6), 3167 - 70
Codon recognition rules in yeast mitochondria; Bonitz SG et al.; The mitochondrial genome of Saccharomyces cerevisiae codes for 24 tRNAs . The nucleotide sequences of the tRNA genes suggest a unique set of rules that govern the decoding of the mitochondrial genetic code . The four codons of unmixed fmilies are recognized by single tRNAs that always have a U in the wobble position of the anticodon . The codons of the mixed families are read by two different tRNAs . Codons terminating in a C or U are recognized by tRNAs with a G and codons terminating in a G or A are recognized by tRNAs with a U in the corresponding positions of the anticodons . There are two exceptions to these rules . In the AUN family for isoleucine and methionine, the isoleucine tRNA has a G and the methionine tRNA has a C in the wobble position . The tRNA for the arginine CGN family also has an A in the wobble position of the anticodon . It is of interest that the CGN codons have not been found in the mitochondrial genes sequenced to date . The simplified decoding system of yeast mitochondria allows all the codons to be recognized by only 24 tRNAs.

Mutat Res, 1980 Jun, 71(1), 67 - 75
Induction of cytoplasmic petite in yeast by guanidine hydrochloride: combined treatment with other inducing agents; Villa LL et al.; We have studied the induction of rho- mutants by guanidine hydrochloride (GuHCl) in combination with other known inducers: ethidium bromide (EB), berenil and ultraviolet light . Competition was observed when cells were simultaneously treated with optimal concentrations of EB and GuHCl; on the other hand, treatment of cells with EB in the presence of non-inducing concentrations of GuHCl resulted in the stimulation of rho- induction of EB . Furthermore, using a strain which upon treatment with high EB concentrations shows recovery of respiratory competence, the presence of GuHCl did not interfere either with the early phase of induction or with the recovery phase, but it did interfere in a competitive fashion with the final irreversible phase of EB induction . In the case of berenil, a synergistic effect was seen when cells were pretreated with GuHCl . A synergistic induction was also observed when cells were submitted to UV prior to GuHCl treatment . These results suggest that GuHCl, EB and berenil act via some common step in their rho- induction pathways . Moreover, GuHCl may somehow be decreasing the efficiency of dark repair of ultraviolet lesions on mitochondrial DNA.

Proc Natl Acad Sci U S A, 1980 Jun, 77(6), 3144 - 8
Association of the 2-micron DNA plasmid with yeast folded chromosomes; Taketo M et al.; The 2-micron DNA plasmid cosedimented in sucrose gradients with the folded chromosome on centrifugation of lysates from logarithmically growing yeast cells . It banded with both the slow-sedimenting g1 form derived from prereplicative cells and the fast-sedimenting g2 form from postreplicative cells . When cells were induced to withdraw from the cell cycle by nitrogen starvation, the folded chromosome was converted to the g0 form, which sedimented more slowly than the g1 form, and only 1/10th the amount of 2-micron DNA cosedimented with this g0 form as compared to the logarithmic-phase forms, g1 and g2 . Expression of the temperature-sensitive cell division cycle (cdc) 28 mutation, which defines the "start" of the cell cycle, resulted in a rapid alteration in the folded chromosome sedimentation pattern, and less than 20% of the 2-micron DNA cosedimented with the folded chromosome . These results raise the possibility that association of the 2-micron DNA plasmid with structures in the cell corresponding to the folded chromosome is subject to cell division cycle control.

Cell, 1980 Jun, 20(2), 507 - 17
Assembly of the mitochondrial membrane system: sequence analysis of a yeast mitochondrial ATPase gene containing the oli-2 and oli-4 loci; Macino G et al.; The mitochondrial DNA (mtDNA) segments of several rho- mutants carrying the oli-2, oli-4 and pho-1 loci have been sequenced . The segments contain a common structural gene sequence that has been identified to include all three genetic markers . The gene codes for a protein with a molecular weight of 28,257 . This new gene is located between 61.5 and 62.6 units on the wild-type map of Saccharomyces cerevisiae and is transcribed from the same DNA strand as most other yeast mitochondrial genes sequenced to date . The amino acid composition and sequence deduced from the DNA sequence indicate that the protein is very hydrophobic, with three long domains (greater than 30 residues) consisting of nonpolar amino acids . Based on its molecular weight, the gene product is tentatively proposed to be either subunit 3 or 6 of the oligomycin-sensitive ATPase.

Biochim Biophys Acta, 1980 May 29, 623(1), 225 - 8
Amino acid sequence of a peptide containing an essential cysteine residue of yeast saccharopine dehydrogenase (L-lysine-forming); Ogawa H et al.; The yeast saccharopine dehydrogenase (L-lysine-forming) contains an essential cysteine residue at the active site which can be carboxymethylated selectively by iodoacetate (Ogawa, H., Okamoto, M . and Fujioka, M . (1979) J . Biol . Chem . 254, 7030--7035) . An undecapeptide containing this residue was isolated from the chymotryptic digest of the carboxymethylated enzyme by gel filtration chromatography and preparative paper electrophoresis . The amino acid sequence of the peptide was determined as Gly-Arg-Cys*-Gly-Ser-Gly-Ala-Leu-Ile-Asp-Leu, by the sequential Edman degradation and digestion with carboxypeptidases.

J Biol Chem, 1980 May 25, 255(10), 4821 - 8
The intracellular proteinases and their inhibitors in yeast . A mutant with altered regulation of proteinase A inhibitor activity; Beck I et al.; A mutation of yeast pai1 has been isolated which leads to altered regulation of proteinase A inhibitor activity . Under conditions of derepression, this mutant as compared with wild type has a 70% reduction in proteinase A inhibitor activity, but no change in the activities of proteinase A or B . The growth of strains carrying the pai1 mutation is sensitive to temperature and pH . The altered physiological and biochemical phenotypes of the mutant appear to be the consequences of a single mutation which segregates 2:2 at meiosis . Results obtained with this mutant indicate that proteinase A and its inhibitor are two independently synthesized polypeptide chains rather than two proteins resulting from proteolytic cleavage of a single precursor . Furthermore, proteinase A and its inhibitor appear to be regulated independently of each other . Studies on the mutant also indicate that the regulation of the proteinase A inhibitor is different from that of the proteinase B inhibitor . In wild type cells there is an excess of proteinase A inhibitor over proteinase A, whereas in the mutant cells there is a 2.5-fold excess of proteinase A over proteinase A inhibitor . This excess proteinase A does not lead to detectable alterations in overall protein degradation . However, tryptophan synthase and proteinase B inhibitor proteins which are sensitive to proteinase A attack in vitro show an enhanced loss of activity in the mutant.

J Biol Chem, 1980 May 25, 255(10), 4468 - 73
In vivo studies on yeast cytochrome c methylation in relation to protein synthesis; Farooqui J et al.; Methylation of cytochrome c was studied in vivo using double label with L-{methyl-3H}methionine and DL-{2-14C}methionine . In pulse-chase experiments the cytochrome c associated with the mitochondrial fraction possessed a higher ratio of 3H/14C label, suggesting the presence of methylated cytochrome c . The appearance of methylated cytochrome c in mitochondria showed no lag phase . The inhibition of cytochrome c methylation in presence of cycloheximide indicated that both the methylation and protein synthesis were tightly coupled and cycloheximide selectively inhibited cytochrome c methylation . There was also an indication of selective turnover of incorporation methyl groups in preformed cytochrome c.

J Biol Chem, 1980 May 25, 255(10), 4957 - 63
Purirication and characterization of two forms of DNA-dependent ATPase from yeast; Plevani P et al.; Two forms of DNA-dependent ATPase activity have been purified from yeast extracts . The two ATPases differ from each other in chromatographic properties and heat stabilities but have similar molecular weight and reaction properties . DNA-dependent ATPase I has been purified to near homogeneity, while DNA-dependent ATPase II is only partially purified . The two ATPases from yeast are related structurally since antiserum raised against ATPase I cross-react against ATPase II . Yeast DNA-dependent ATPase I has a native molecular weight of about 68,000 and consists of a single polypeptide chain . ATPase II also sediments on sucrose gradient as a 68,000-dalton protein . Both yeast DNA-dependent ATPases hydrolyze dNTPs and rNTPs to their corresponding nucleoside diphosphates and orthophosphate, but dATP and ATP are preferred substrates . In addition to nucleoside triphosphates, both enzymes require a divalent cation and a polynucleotide for activity . Single-stranded DNAs and polydeoxynucleotides are the most effective co-substrates for yeast DNA-dependent ATPases . Addition of yeast DNA-dependent ATPases to DNA synthesis system containing yeast DNA polymerases does not significantly stimulate the rate of DNA synthesis.

Nucleic Acids Res, 1980 May 24, 8(10), 2307 - 29
Yeast tRNAPhe conformation wheels: a novel probe of the monoclinic and orthorhombic models; Srinivasan AR et al.; A series of conformation wheels is constructed from the recently refined X-ray crystallographic data of monoclinic and orthorhombic yeast tRNAPhe . These circular plots relate the primary chemical structure (i.e., base sequence) directly to the secondary and tertiary structure of the molecule . The circular sequence of backbone torsion angles displays a unique pattern that is useful both in distinguishing the ordered and disordered regions of the molecule and in comparing the three sets of experimental data . Composite conformation wheels describe the fluctuations in the "fixed" parameters (phi', phi, chi) and independent conformation wheels reveal the changes in the "variable" parameters (omega', omega, psi, psi') of the three different yeast tRNAPhe models . Additional plots of base-stacking parameters help to visualize the intimate interrelationship between chemical sequence and three-dimensional folding of yeast tRNAPhe . The composite data illustrate several conformational schemes that position the bases of adjacent nucleosides in a parallel stacked array and reveal an even larger number of conformations that introduce bends or turns in the polynucleotide chain.

J Membr Biol, 1980 May 23, 54(2), 149 - 56
Some characteristics of Ca2+ uptake by yeast cells; Borbolla M et al.; Experiments were performed to obtain information on: (i) the specific properties of Ca2+ binding and transport in yeast; (ii) the relationship between both parameters; (iii) similarities to or differences from other biological systems as measured by the effects of inhibitors; and (iv) the effects of mono and divalent cations, in order to get some insight on the specificity and some characteristics of the mechanism of the transport system for divalent cations in yeast . The results obtained gave some kinetic parameters for a high affinity system involved in the transport of Ca2+ in yeast . These were obtained mainly by considering actual concentrations of Ca2+ in the medium after substracting the amounts bound to the cell . A km of 1.9 microM and a Vmax of 1.2 nmol (100 mg.3 min)-1 were calculated . The effects of some inhibitors and other cations on Ca2+ uptake allow one to postulate some independence between binding and transport for this divalent cation . Of the inhibitors tested, only lanthanum seems to be a potent inhibitor of Ca2+ uptake in yeast . The effects of Mg2+ on the uptake of Ca2+ agree with the existence of a single transport system for both divalent cations . The actions of Na+ and K+ on the transport of Ca2+ offer interesting possibilities to study further some of the mechanistic properties of this transport system for divalent cations.

Experientia, 1980 May 15, 36(5), 587 - 8
Candida utilis as a convenient and safe substitute for the pathogenic yeast C . albicans in Daniels' phototoxicity test; Kagan J et al.; Candida utilis is a safe and convenient substitute for the pathogenic yeast C . albicans in phototoxicity tests . With both organisms 8-methoxypsoralen and a-terthienyl give positive results while photodynamic compounds give negative results.

Biochemistry, 1980 May 13, 19(10), 2005 - 16
Transition-state structure in the yeast alcohol dehydrogenase reaction: the magnitude of solvent and alpha-secondary hydrogen isotope effects; Welsh KM et al.; Solvent and alpha-secondary isotope effects have been measured in the yeast alcohol dehydrogenase reaction, under conditions of a rate-limiting transfer of hydrogen between coenzyme and substrate . Determination of catalytic constants (at saturating concentrations of substrate and coenzyme) in H2O and D2O as a function of pH(D) has allowed the separation of solvent effects on pKa from kcat: delta pKa = pKD--pKH = 0.02--0.21, kH2O/kD2O = 1.20 +/- 0.09 in the direction of p-methoxybenzyl alcohol oxidation, and kH2O/kD2O = 0.50 +/- 0.05 and 0.58 +/- 0.06 for p-methoxybenzaldehyde reducation by NADH and {4-2H}NADH . The small effect of D2O on pKa, which contrasts with the common observation that delta pKa congruent to 0.4--0.6, is tentatively assigned to ionization of an active-site ZnOH2 . The near absence of an isotope effect on kcat in the direction of alcohol oxidation rules out a mechanism involving concerted catalysis by an active-site base of hydride transfer . In the direction of aldehyde reduction, the observation of inverse isotope effects on kcat is concluded to reflect displacement of zinc-bound water by substrate to form an inner-sphere complex, subsequent to the E.S complex . Equilibrium alpha-secondary isotope effects, measured as a frame of reference for kinetic values, indicate KH/KT = 1.33 +/- 0.05 and 1.34 +/- 0.09 for the oxidation of {1(S)-3H}benzyl alcohol and p-methoxy{1(S)-3H}benzyl alcohol, respectively . Kinetic alpha-secondary isotope effects are within experimental error of equilibrium values, kH/kT = 1.34 +/- 0.07 and 1.38 +/- 0.02 for {1(S)-3H}benzyl alcohol and p-methoxy{1(S)-3H}benzyl alcohol oxidation, respectively . The near identity of kinetic and equilibrium alpha-secondary isotope effects in the direction of alcohol oxidation implicates a transition-state structure which resembles aldehyde with regard to bond hybridization properties . This result contrasts sharply with previously reported structure--reactivity correlations, which implicate a transition-state structure resembling alcohol with regard to charge properties . The significance of these findings to the mechanism of NAD(P)H-dependent redox reactions is discussed.

Nucleic Acids Res, 1980 May 10, 8(9), 1975 - 86
Structure of a yeast non-initiating methionine-tRNA gene; Olah J et al.; 4 to 8 kb Hind III fragments of yeast DNA were cloned into pBR322 . One of these clones (pY6m3) containing a single tRNA3Met gene has been characterized in detail . The DNA sequence of the structural gene is colinear with the tRNA sequence, which means that in this case no intervening sequence is present . The 5'-leader and 3'-trailer sequences have also been determined . The 5'-flanking region can be folded up into possible secondary structures.

Biochim Biophys Acta, 1980 May 7, 629(2), 217 - 24
Effect of acriflavine on the hexokinase isozyme pattern of a yeast, Hansenula jadinii; Kimura A et al.; Dried cells of a yeast, Hansenula jadinii, that had been cultured aerobically with acriflavine, contained three hexokinase isozymes and metabolized glucose at 0.6 M to produce ATP to phosphorylate nucleotides in the presence of a high concentration of phosphate . Dried cells cultured aerobically without acriflavine contained two hexokinase isozymes and could not metabolize glucose under the same conditions . Two of the isozymes of the yeast cultured with acriflavine were similar to isozymes of the yeast cultured without acriflavine . However, the third isozyme was resistant to a high phosphate concentration and caused regeneration of ATP through glycolysis and phosphorylation of nucleotides.

Mikrobiologiia, 1980 May-Jun, 49(3), 452 - 8
{Cytochrome P-450 induction during yeast organism growth on various substrates}; Il'chenko AP et al.; The induction of cytochrome P-450 was studied in Torulopsis candida and other yeast species in the process of their growth on glucose, hexadecane, ethanol, hexadecanol and palmitate . Cytochrome P-450 was induced in all of the studied alkane oxidizing yeast strains during their growth on hexadecane or on the intermediates of its oxidation, viz . hexadecanol and palmitate . However, the maximal content of P-450 in the cells was 3-4 times lower during the growth on hexadecanol and palmitate as compared to the growth on hexadecane . In Candida utilis incapable of growing on n-alkanes but growing on hexadecanol and palmitate, cytochrome P-450 was not detected upon the yeast growth on these substrates . Cytochrome P-450 was not induced in any of the strains during their growth on ethanol . In the course of growth on glucose, cytochrome P-450 was found only in T . candida; it was induced in its cells just prior to the stationary phase caused by the exhaustion of the carbon source.

Genetics, 1980 May, 95(1), 63 - 80
Heteroduplex repair as an intermediate step of UV mutagenesis in yeast; Eckardt F et al.; We have measured UV-induced mutation frequencies in yeast in a forward, nonselective assay system by scoring white adex ade2 double auxotrophs among parental red-pigmented ade2 clones . The frequencies of sectored and pure mutant clones were determined separately . In excision-defective strains carrying the genes rad1-1, rad3-2 and rad4-4, as well as in the double mutants, rad 1-1 rad 3-2 and rad 1-1 rad 4-4, considerably more sectored than pure clones are induced in the low-dose range; in repair-competent strains, pure mutant clones substantially outnumber the sectored clones . These results can be explained on the basis of known differences in the timing of error-prone repair during the cell division cycle; that is, we assume that error-prone repair occurs primarily before replication in RAD wild-type strains but after replication in excision-deficient mutants . It has been suggested that excision deficiency has a pleiotropic effect on heteroduplex repair and nucleotide excision repair; however, the high percentage (36.6%) of half-sectored clones found in the rad1-1 strain is hard to reconcile with this hypothesis . We propose that heteroduplex repair occurs subsequent to error-prone repair in both excision-proficient and excision-deficient strains.

Cell, 1980 May, 20(1), 207 - 14
Splice point sequence and transcripts of the intervening sequence in the mitochondrial 21S ribosomal RNA gene of yeast; Bos JL et al.; By S1 nuclease mapping we have located the intervening sequence in the large ribosomal RNA gene of Saccharomyces cerevisiae omega+ strains 570 bp from the 3' end of the rRNA gene . No intervening sequence was detected at this position in S . carlsbergensis, but the sequences of the mature 21S rRNAs of these two strains appear to be identical in this region . By comparing the DNA sequence of the region of the intervening sequence in an omega+ strain with the corresponding sequence in S . carlsbergensis, we have determined the splice points of the 21S rRNA gene . These sequences show no homology with splice points in nuclear and viral genes or with the splice points in the chloroplast 23S rRNA gene of Chlamydomonas . The external borders of the splice points have a complementary sequence in the intervening sequence . The largest transcript hybridizing with the probe of the intervening sequence has a size corresponding to that expected for an rRNA precursor still containing the intervening sequence; the smallest transcript corresponds in size to the intervening sequence itself.

Cell, 1980 May, 20(1), 173 - 83
Mutations affecting RNA splicing and the interaction of gene expression of the yeast mitochondrial loci cob and oxi-3; Van Ommen GJ et al.; In Saccharomyces cerevisiae strains KL14-4A and 777-3A, four intervening sequences of 1900 (l alpha beta), 1400 (l beta gamma), 1300 (l gamma delta) and 650 bp (l delta epsilon) separate the five coding sequences (alpha-epsilon) of the structural gene (cob) for cytochrome b . Its major transcript is an 18S RNA (2200 nucleotides) which is likely to be the functional mRNA . The lengths of a series of larger transcripts and their hybridization with probes specific for different intervening sequences are consistent with their being intermediates in a splicing process which generates 18S RNA from a giant primary transcript (greater than or equal to 7.5 kb) covering the whole cob region . There is no absolute order of splicing . The intervening sequence l alpha beta is excised in two stages . The first generates a stable 10S RNA, coded for by sequences immediately downstream of the 18S RNA coding segment alpha . The function of this RNA is unknown . Its excision is an early step in processing, whereas excision of the remainder of l alpha beta is a late event . We have studied four cytochrome b-deficient mutants . These map in intervening sequences and are splicing-defective . They accumulate 22S-28S RNAs which contain one or more intervening sequences . The l alpha beta mutants synthesize long, novel polypeptides, antigenically related to cytochrome b, possibly as a result of read-through into the intervening sequences . Several cob mutants also display alterations in their transcripts of oxi-3, the locus which codes for cytochrome c oxidase subunit I . This indicates that interactions between cob and oxi-3 exist at the level of RNA processing.

J Bacteriol, 1980 May, 142(2), 608 - 14
Stimulation of yeast ascospore germination and outgrowth by S-adenosylmethionine; Brawley JV et al.; The supplementation of S-adenosylmethionine (SAM) to germination medium stimulated the accumulation of {14C}uracil from the medium into germinating cells, as well as its incorporation into ribonucleic acid during germination and outgrowth of ascospores of Saccharomyces cerevisiae . In addition to uracil, the accumulation of leucine, cytosine, serine, and methionine was also stimulated by the extracellular addition of this sulfonium compound . The SAM-stimulatory effect was dose dependent; half-maximal stimulation was observed at about 50 muM . The effect exerted by SAM supplementation appeared to be specific for SAM and for germination and outgrowth . In the absence of SAM biosynthesis (in the presence of cycloleucine), spores were inhibited in their ability to accumulate label, whereas the supplementation of SAM completely reversed the cycloleucine-induced inhibition of accumulation . In addition to accumulation and incorporation, the kinetics of bud formation during outgrowth were also stimulated by exogenous SAM . The stimulation of budding by SAM was amplified in an ethionine-resistant strain . These observations suggest that SAM may be essential for the initiation of cell division during the breaking of spore dormancy.

J Cell Biol, 1980 May, 85(2), 199 - 212
Distribution of chitin in the yeast cell wall . An ultrastructural and chemical study; Molano J et al.; The distribution of chitin in Saccharomyces cervisiae primary septa and cell walls was studied with three methods: electron microscopy of colloidal gold particles coated either with wheat germ agglutinin or with one of two different chitinases, fluorescence microscopy with fluorescein isothiocyanate derivatives of the same markers, and enzymatic treatments of {14C}glucosamine-labeled cells . The septa were uniformly and heavily labeled with the gold-attached markers, an indication that chitin was evenly distributed throughout . To study the localization of chitin in lateral walls, alkali-extracted cell ghosts were used . Observations by electron and fluorescence microscopy suggest that lectin-binding material is uniformly distributed over the whole cell ghost wall . This material also appears to be chitin, on the basis of the analysis of the products obtained after treatment of 14C-labeled cell ghosts with lytic enzymes . The chitin of lateral walls can be specifically removed by treatment with beta-(1 leads to 6)-glucanase containing a slight amount of chitinase . During this incubation approximately 7% of the total radioactivity is solubilized, about the same amount liberated when lateral walls of cell ghosts are completely digested with snail glucanase yield primary septa . It is concluded that the remaining chitin, i.e., greater than 90% of the total, is in the septa . The facilitation of chitin removal from the cell wall by beta-(1 leads to 6)-glucanase indicates a strong association between chitin and beta-(1 leads to 6)-glucan . Covalent linkages between the two polysaccharides were not detected but cannot be excluded.

Prikl Biokhim Mikrobiol, 1980 May-Jun, 16(3), 347 - 50
{Alpha-galactosidase producers among yeast cultures}; Ulezlo IV et al.; The capacity for biosynthesis of alpha-galactosidase was examined in 89 yeast cultures belonging to 21 genera during submerged cultivation on a medium containing dry whey . This capacity was found only in one genus, namely Schwanniomyces . Optimal cultivation conditions were selected for the strain Schw . alluvius 1167 that showed the highest alpha-galactosidase activity . As a result, activity of alpha-galactosidase was increased 4.8 times as compared with the initial level.

Cell, 1980 May, 20(1), 215 - 22
Mutants of yeast initiating translation of iso-1-cytochrome c within a region spanning 37 nucleotides; Sherman F et al.; We used a specially constructed strain, cyc1-345, of the yeast Saccharomyces cerevisiae to isolate revertants that initiated translation of iso-1-cytochrome c at various sites along an extended region of the mRNA . Normal amounts of iso-1-cytochrome c occurred when translation initiated at the abnormal sites corresponding to amino acid positions -3, -2, 3 and 5, as well as the normal position -1; 20% of the normal amounts occurred when translation initiated at the abnormal position 9 . These results with cyc1-345 revertants indicate that translation of iso-1-cytochrome c can initiate with the normal efficiency at any site within the region spanning 25 nucleotides . Furthermore, because the lower amount of the short iso-1-cytochrome c in the mutant initiating at position 9 may not necessarily reflect an inefficiency of translation, we believe that translation can initiate with normal or near-normal efficiencies at any site within a 37 nucleotide region, and presumably at any site preceding and following that of the normal initiation codon . These results establish that there is no absolute requirement for a particular sequence 5' to the initiation codon, and are consistent with our previous suggestion that translation starts at the AUG codon closest to the 5' end of the mRNA.

Can J Biochem, 1980 May, 58(5), 405 - 9
Yeast, rye, and calf histones . Similarities and differences detected by electrophoretic and immunological methods; Tessier A et al.; Yeast histones H2A, H2B, and H3 were purified using the standard histone purification procedures of differential solubility and exclusion chromatography . Yeast histone H4 was isolated by the same methods in a fraction containing one other major protein component . The four yeast core histones were identified by their reactions with antisera against rye and (or) calf histone fractions as well as by their electrophoretic, chromatographic, and solubility properties . The immunological distances between yeast H2B and rye and calf H2B fractions are substantial, as is the rye-calf distance for H2B . The immunological distance between yeast H2A and rye H2A is also large and is similar to the rye H2A - calf H2A distance . On the other hand, the immunological distance between yeast H3 and rye and calf H3 is much greater than that between rye H3 and calf H3 . These and other results indicate that yeast H3 differs appreciably from the H3 of higher eucaryotes.

Cell, 1980 May, 20(1), 185 - 97
Sequence of the intron and flanking exons of the mitochondrial 21S rRNA gene of yeast strains having different alleles at the omega and rib-1 loci; Dujon B; The complete nucleotide sequence has been determined for the intron, its junctions and the flanking exon regions of the 21S rRNA gene in three genetically characterized strains differing by their omega alleles (omega+, omega- and omega n) and by their chloramphenicol-resistant mutations at the rib-1 locus . Comparison of these DNA sequences shows that: --omega+ differs from omega- and omega n by the presence of the intron (1143 bp), as well as by a second and unexpected mini-insert (66 bp) located 156 bp upstream within the exon, whose nature and functions are still unknown but whose striking palindromic structure may suggest a mitochondrial transposable element . --The two mutations C321R and C323R correspond to two different monosubstitutions, 56 bp apart in the omega- and omega n strains but separated by the intron in the omega+ strains . In relation to previous genetic results, a model is discussed assuming that the interactions of two different regions or genetic loci determine the chloramphenicol resistance, one of which contains the omega n mutations . --A long uninterrupted coding sequence able to specify a 235 amino acid polypeptide exists within the intron . This remarkable observation gives new insight into the origin of the mitochondrial introns and raises the question of the possible functions of intron-encoded polypeptides . Finally, sequence comparisons with evolutionarily distant organisms, showing that different rRNA introns are inserted at different positions of an otherwise highly conserved region of the gene, suggest a recent insertion of these introns and a mechanism for splicing after the assembly of the large ribosomal subunit.

Thorax, 1980 Apr, 35(4), 282 - 5
Defective yeast opsonisation of serum in sarcoidosis; Johnson NM et al.; We have studied the opsonising ability of the sera of 49 patients with sarcoidosis . The serum of 11 (22%) patients was defective in this ability, whereas only two (4%) of 46 clinic control subjects and three (7%) of 43 laboratory control subjects showed this defect . The difference between the prevalence of the defect in sarcoidosis and the control groups was statistically significant (p less than 0.01) . Although the patients with sarcoidosis who had this defect tended to have pulmonary infiltration, this relationship was not statistically significant . Similarly, there was no correlation between the activity of sarcoidosis and this defect, although there was a significant (p less than 0.05) relationship between the opsonising defect and the persistence of circulating immune complexes . Serum opsonisation is a genetically linked host defense mechanism . Our findings suggest that the presence of this serum defect may render a person more susceptible to sarcoidosis.

Eur J Biochem, 1980 Apr, 105(2), 259 - 66
Structural studies on yeast 3-phosphoglycerate kinase . Identification by immuno-affinity chromatography of one glutamyl residue essential for yeast 3-phosphoglycerate kinase activity . Its location in the primary structure; Desvages G et al.; 3-Phosphoglycerate kinase is inactivated by 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate and nitrotyrosine ethyl ester . The coupling of 1 mol nitrotyrosine/mol enzyme is sufficient to inactivate the protein completely . A weak protection against inactivation is observed with each substrate added separately . In contrast, the complex ATP--3-phosphoglycerate--enzyme or ATP--Mg--3-phosphoglycerate--enzyme affords a considerable protection . The critical residue is identified as a glutamyl residue after isolation by immuno-affinity chromatography of nitrotyrosyl peptide resulting from exhaustive proteolytic digestion of the modified protein . In addition, the determination of the primary sequence of the C-terminal part of the protein leads to the location of the glutamyl residue at position eight from the C-terminus . We conclude that this glutamyl residue is situated in the domain which does not bind the nucleotide substrates {Bryant, T.N., Watson, H.C . and Wendell, P.L . (1974) Nature (Lond.) 247, 14--17} . Its role in the catalysis process is discussed.

Cell, 1980 Apr, 19(4), 923 - 33
Yeast viral double-stranded RNAs have heterogeneous 3' termini; Bruenn JA et al.; The yeast virus, ScV, is communicated only by mating . It has two separately encapsidated dsRNAs . One of these, L, codes for the major capsid polypeptide . The other, M, codes for a polypeptide toxic to yeasts without ScV-M particles . Defective interfering particles containing fragments of M (S) displace ScV-M when they arise . We have shown that five independently isolated S dsRNAs are all derived by internal deletion of M . The 3' ends of all the ScV dsRNAs are markedly heterogeneous . For instance, half of the first 35 nucleotides at one 3' end of M and S are variable . Conserved sequences at the 3' ends of M and S are AAACACCCAUCAOH and AUUUCUUUAUUUUUCAOH . Conserved sequences at the 3' ends of L are UAAAAAUUUUUCAOH and AAAAAUXCAOH, where X is variable . We propose that the sequence AUUUUUCAOH is a recognition sequence for the capsid-associated single-stranded RNA polymerase activity . Since all the viral RNAs have pppGp 5' termini, their 3' termini probably extended one nucleotide beyond the terminal pppGp.

Eur J Biochem, 1980 Apr, 105(3), 509 - 15
Yeast mannosyl transferases requiring dolichyl phosphate and dolichyl phosphate mannose as substrate . Partial purification and characterization of the solubilized enzyme; Babczinski P et al.; The first mannosyl unit of manno-oligosaccharides of fungal mannoproteins is transferred in a dolichyl-phosphate-dependent reaction sequence to serine/threonine residues of the protein . The two membrane-bound enzymes catalyzing this transfer in the yeast Saccharomyces cerevisiae have been solubilized by detergents . The enzyme transferring mannose from guanosine diphosphate mannose to dolichyl phosphate has been purified 18-fold when based on membrane protein and 140-fold when based on total cell protein . The enzyme transferring mannose from dolichyl phosphate mannose to protein has been purified 48-fold and 380-fold, respectively . A HCl-treated cell-wall mannoprotein from yeast served as acceptor protein for the second enzyme . The solubilized enzyme catalyzing the formation of dolichyl diphosphate mannose has a Km for guanosine diphosphate mannose of 7 x 10(-6) M and is saturated with about 0.15 mM yeast dolichyl phosphate . The metal requirement, pH-optima, and the detergent concentration necessary for optimal activity have been determined for both solubilized enzymes.

Biophys Chem, 1980 Apr, 11(2), 265 - 9
Hydrophobic binding is not an independent stereochemical determinant in the yeast glyoxalase I reaction; Creighton DJ et al.; For yeast glyoxalase I, a stereospecific proton-transfer mechanism requires the formation of either a cis or a trans-enediol intermediate . Analogs of the two possible isometric enediol intermediates, formed from the hemimercaptal due to phenylglyoxal and glutathione, have been synthesized in which the oxygen atoms of the enediol are replaced by protons . Both isomeric analogs are strong linear competitive inhibitors of the enzyme having nearly equal inhibition constants: Ki(cis) = 0.10 mM; Ki(trans) = 0.16 mM . This suggests that while hydrophobic interactions between substrate, enediol intermediate and enzyme may contribute significantly to binding, this type of interaction is not an independent stereochemical determinant of the reaction.

Biophys Chem, 1980 Apr, 11(2), 239 - 48
Time resolved spectroscopy of tryptophyl fluorescence of yeast 3-phosphoglycerate kinase; Privat JP et al.; The tryptophyl fluorescence emission of yeast 3-phosphoglycerate kinase decreases from pH 3.9 to pH 7.2 following a normal titration curve with an apparent pK of 4.7 . The fluorescence decays have been determined at both extreme pH by photocounting pulse fluorimetry and have been found to vary with the emission wavelength . A quantitative analysis of these results according to a previously described method allows to determine the emission characteristics of the two tryptophan residues present in the protein molecule . At pH 3.9, one of the tryptophan residues is responsible for only 13% of the total fluorescence emission . This first residue has a lifetime tau 1 = 0.6 ns and a maximum fluorescence wavelength lambda 1max = 332 nm . The second tryptophan residue exhibits two lifetimes tau 21 = 3.1 ns and tau 22 = 7.0 ns (lambda 2max = 338 nm) . In agreement with the attribution of tau 21 and tau 22 to the same tryptophan residue, the ratio beta = C21/C22 of the normalized amplitudes is constant along the fluorescence emission spectrum . At pH 7.2, the two tryptophan residues contribute almost equally to the protein fluorescence . The decay time of tryptophan 1 is 0.4 ns . The other emission parameters are the same as those determined at pH 3.9 . We conclude that the fluorescence quenching in the range pH 3.9 to pH 8.0 comes essentially from the formation of a non emitting internal ground state complex between the tryptophan having the longest decay tie equilibrium constant of the internal complex can be estimated . The quenching group is thought to be a carboxylate anion . Excitation transfers between the two tryptophyl residues of the protein molecule appear to have a small efficiency.

J Histochem Cytochem, 1980 Apr, 28(4), 311 - 5
Glutaraldehyde nonfixation of isolated viral and yeast RNAs; Langenburg WG; The RNAs of brome mosaic (BMV), barley stripe mosaic (BSMV), and tobacco mosaic (TMV) viruses were inactivated by reaction with buffered glutaraldehyde . Glutaraldehyde did not fix 4% BMV-RNA, 20% t-RNA, 5% polyadenylic acid, or 5% adenosine monophosphate into water-insoluble precipitates, or gels, in distilled water or in low or high ionic strength buffers nor did it change their ultraviolet (UV) spectra . Two SDS- and phenol-purified commercial yeast RNA preparations from different sources gave UV spectra typical of pure RNA, but could not be freed of a contaminant that reacted with glutaraldehyde by forming a precipitate . The yeast RNAs did not become water-insoluble after glutaraldehyde reaction . BMV-RNA precipitated by Mg2+ could not be cross-linked into an insoluble form by glutaraldehyde . Nonfixation of RNA by glutaraldehyde must be considered in interpretation of attempts to localize RNA by electron microscopy.

Genetics, 1980 Apr, 94(4), 891 - 8
Dependence on mating type for the overproduction of iso-2-cytochrome c in the yeast mutant CYC7-H2; Rothstein RJ et al.; The CYC7-H2 mutation causes an approximately 20-fold overproduction of iso-2-cytochrome c in a and alpha haploid strains of the yeast Saccharomyces cerevisiae due to an alteration in the nontranslated regulatory region that is presumably contiguous with the structural region . In this investigation, we demonstrated that heterozygosity at the mating type locus, a/alpha or a/a/alpha/alpha, prevents expression of the overproduction, while homozygosity, a/a and alpha/alpha, and hemizygosity, a/0 and alpha/0, allow full expression of the CYC7-H2 mutation, equivalent to the expression observed in a and alpha haploid strains . There is no decrease in the overproduction of iso-2-cytochrome c in a/alpha diploid strains containing either of the other two similar mutations, CYC7-H1 and CYC7-H3 . It appears as if active expression of one or another of the mating-type alleles is required for the overproduction of iso-2-cytochrome c in CYC7-H2 mutants.

Proc Natl Acad Sci U S A, 1980 Apr, 77(4), 2119 - 23
Isolation of genes by complementation in yeast: molecular cloning of a cell-cycle gene; Nasmyth KA et al.; cdc28, one of several genes required for cell division in the yeast Saccharomyces cerevisiae, has been isolated on recombinant plasmids . A recombinant plasmid pool containing the entire yeast genome was constructed by partial digestion of yeast DNA with the four-base recognition restriction endonuclease Sau3A to give the equivalent of random fragments, size selection on sucrose gradients, and introduction of the fragments into the yeast vector YRp7 by use of the homology of Sau3A ends with those generated in the vector by cleavage with BamHI . Recombinant plasmids capable of complementing cdc28 mutations were isolated by transformation of a cdc28ts strain and selection for clones capable of growth at the restrictive temperature . Plasmids responsible for complementing the cdc28ts phenotype were shown to recombine specifically with the chromosomal cdc28 locus, confirming the identity of the cloned sequences . In addition, one of the recombinant plasmids was capable of complementing a mutation in tyr1, a gene genetically linked to cdc28 . This method of gene isolation and identification should be applicable to all yeast genes for which there are readily scorable mutants.

Proc Natl Acad Sci U S A, 1980 Apr, 77(4), 1898 - 902
Yeast mating pheromone alpha factor inhibits adenylate cyclase; Liao H et al.; The pheromone alpha factor, secreted by Saccharomyces cerevisiae cells of the alpha mating type, serves to synchronize the opposite mating type (a cells) at G1 as a prelude to fusion of the two cell types . We found that, in vitro, alpha factor inhibited the membrane-bound adenylate cyclase of these cells in a dose-dependent manner . Moreover, one class (ste5) of a cell mutants that grow normally at either 23 degrees or 34 degrees C but that are unable to respond to alpha factor or to mate at the higher temperature possessed an adenylate cyclase activity that was not inhibited by alpha factor at 34 degrees C but was fully sensitive to inhibition at 23 degrees C . Furthermore, addition of cyclic AMP to a cell culture medium shortened the period of pheromone-induced G1 arrest . We conclude that inhibition of adenylate cyclase activity by alpha factor may constitute, at least in part, the biochemical mode of action of the pheromone in vivo.

Biull Eksp Biol Med, 1980 Apr, 89(4), 439 - 41
{Macrophage activation by polysaccharides from yeast-like fungi}; Kashkina MA et al.; The effect of polysaccharides isolated from yeast-like fungi on diverse activities of murine peritoneal macrophages was studied in experiments in vitro . Yeast polysaccharides had a nonspecific activating effect on macrophages in tissue culture . They enhance the adhesion of macrophages to glass, stimulate phagocytosis and intracellular digestion, and change the chemotactic activity . The activity of polysaccharides directly correlates with their molecular weight . There is a relationship between the biological activity and chemical structure of polysaccharides . The beta-structural polysaccharides are capable of activating the functions of macrophages, while beta-structural dextrans do not possess such properties.

J Biol Chem, 1980 Mar 25, 255(6), 2624 - 7
The relation of heme to catalase apoprotein synthesis in yeast; Woloszczuk W et al.; The synthesis of two hemoproteins, catalase A and catalase T, was studied in mutants of Saccharomyces cerevisiae deficient in heme formation . These mutants can be grown on the end-product heme or on a heme precursor, or on ergosterol and Tween 80 (a source of oleic acid) . It was found by immunoprecipitation that, in the presence of heme, catalases A and T were present in the mutants, but that in its absence (growth on ergosterol and Tween 80) the apoproteins of these enzymes were not detectable . In contrast, cytochrome c peroxidase, and some of the subunits of cytochrome c oxidase are present in cells grown without heme (Saltzgaber-Muller, J., and Schatz, G . (1978) J . Biol . Chem . 253, 305-310) . Other evidence suggests that absence of catalase T apoprotein under heme-less conditions may be due to control by heme of apoprotein synthesis (G . Ammerer and H . Ruis, unpublished results), rather than increased proteolytic degradation.

J Biol Chem, 1980 Mar 25, 255(6), 2596 - 605
Structural comparison of two nontandemly repeated yeast glyceraldehyde-3-phosphate dehydrogenase genes; Holland JP et al.; A hybrid plasmid (pgap63) was isolated which contains a second yeast glyceraldehyde-3-phosphate dehydrogenase structural gene . The complete nucleotide sequence of this gene was determined and compared with the primary structure of a yeast glyceraldehyde-3-phosphate dehydrogenase gene (pgap49) which was reported previously (Holland, J.P., and Holland, M.J . (1979) J . Biol . Chem . 254, 9839-9845) . Based on the restriction endonuclease cleavage maps of the isolated segments of yeast DNA which contain these genes, the two genes are nontandemly duplicated . Greater than 94% of the nucleotides within the coding regions of these genes are homologous and the polypeptides encoded by the two structural genes differ by only 15 amino acid residues . Both genes have the same, highly biased, codon usage pattern and neither contains intervening sequences . Approximately 100 nucleotides adjacent to the ATG initiation codons and 130 nucleotides beyond the TAA termination codons are greater than 70% homologous . Structures within the flanking sequences of the genes which are potentially relevant to transcriptional and translational control are described . Several sequences (8 to 15 nucleotides in length) are repeated in both the 5' and 3' flanking sequences of the genes in a noninverted fashion . Finally, a rapid procedure for the isolation of spontaneous deletions within hybrid plasmid DNAs is described, as is the isolation of a structural gene deletion in pgap49.

C R Seances Acad Sci D, 1980 Mar 17, 290(11), 695 - 8
{Primary structure of yeast mitochondrial tryptophan-tRNA capable of translating the termination U-G-A codon}; Sibler AP et al.; The primary structure of Yeast Saccharomyces cerevisiae mitochondrial tryptophane-tRNA, isolated by reversed phase chromatography and two-dimensional gel electrophoresis has been determined . It is as follows: pA-A-G-G-A-U-A-U-A-G-U-U-U-A-A-D-G-G-D-A-A-A-A-C-A-G-U-U-G-A-psi-U-U-C-A-i6 A (ms2i6 A)-A-psi-C-A-A-U-C-A-U-U-A-G-G-A-G-T-psi-C-G-A-A-U-C-U-C-U-U-U-A-U-C-C-U-U-G-C-C-A . Owing to its anticodon U-C-A-, where U represents a modified uridine, this tRNA can translate the opal codon U-G-A, which is usually a protein synthesis termination codon in cytoplasmic systems.

Biochim Biophys Acta, 1980 Mar 13, 596(3), 381 - 92
Interaction of monovalent cations with Rb+ and Na+ uptake in yeast; Derks WJ et al.; The concentration dependence of both Rb+ uptake and Na+ uptake by yeast can be described by a quadratic rate equation . This equation is derived for translocation of cations via a two-site translocation system . In accordance with predictions made for such a two-site translocation system the shape of the uptake isotherm depends both upon the substrate cation species and upon the concentration of other added competing cations . On plotting the rate of Rb+ uptake against the quotient of that rate and the Rb+ concentration concave, convex and also linear curves are found depending upon the type and the concentration of added monovalent cations . The Na+ uptake isotherm plotted in a similar way shows a shift from a concave curve to a straight line on adding increasing amounts of Rb+ to the yeast suspension . Decreasing the pH of the medium leads to a more pronounced convex uptake isotherm for Rb+ uptake . This can be ascribed to an indirect effect of the surface potential upon Rb+ uptake and to occupation of the binding sites by protons, which are replaced again by Rb+ at increasing Rb+ concentrations . Replacement of one sodium ion from one of the two sites of the monovalent cation transport system by either K+ OR Rb+ leads to an increase in the rate of Na+ translocation across the yeast cell membrane.

Nucleic Acids Res, 1980 Mar 11, 8(5), 1061 - 79
The electrostatic molecular potential of yeast tRNAPhe . (I) . The potential due to the phosphate backbone; Lavery R et al.; We present a preliminary theoretical study of the electrostatic potential surrounding yeast tRNAPhe by computing the component of this potential due to all the 76 phosphate groups of the molecule . The general features of the results obtained are discussed and deductions concerning the binding of Mg2+ ions to the molecule in relation to the potential are presented.

Mikrobiologiia, 1980 Mar-Apr, 49(2), 331 - 4
{Yeast cultivation on the water-soluble oxidation products of brown coal}; Bazarova OV et al.; The object of this work was to find out whether a mixture of organic acids produced at the first and second stages of lignite oxidation can be used as a substrate for cultivating six yeast cultures belonging to the Candida genus . Succinic acid has been shown to be the best accumulated component in the mixture . When C . guilliermondii VSB-249 was cultivated on succinic acid, its growth was inhibited by alpha-naphthoic acid, 1,2-naphthalene dicarboxylic acid and isophthalic acid . It might be concluded therefore that a mixture of acids produced at the first atage of oxidation can serve as the source of carbon for Candida since it contains less inhibitors than a mixture of acids produced at the second stage of lignite oxidation.

Prikl Biokhim Mikrobiol, 1980 Mar-Apr, 16(2), 149 - 55
{Assimilation of n-alkanes with a varying length of the carbon chain by the yeast Candida guilliermondii}; Demanova NF et al.; Using radioactive tracers, the effect of n-alkanes with a varying length--C16-C25--of the carbon chain on the rate of yeast growth and the ratio of major chemicals in their biomass was studied . The change in the level of n-alkanes accumulated by the yeast during carbon starvation was determined . No differences in the rate of metabolization of 1-14C-octadecane, 1,2-3H-hexadecane, and 13-14C-pentacosane were found . During 3 hour incubation the cell losses of C25, C18 and C16 amounted to 35.0, 33.0 and 38.1 microgram alkane/mg yeast, respectively . The intensity of yeast growth in the accumulative culture on dispersed n-alkanes with different molecular weights was similar . The specific formation of CO2 during the lag-phase by the yeast cultivated C18 was larger than on C23 or C25 . The lipid content in the yeast grown on C18 was 3 times greater than in those grown on C22 . The difference was made by an increased content of triglycerides and waxes.

Cell, 1980 Mar, 19(3), 741 - 51
Processing of intervening sequences: a new yeast mutant which fails to excise intervening sequences from precursor tRNAs; Hopper AK et al.; By using conditional loss of suppression an an assay, we have been successful in screening for a yeast mutant which is defective in tRNA processing . The los1-1 mutation causes an accumulation of a subset of precursor tRNAs at the nonpermissive temperature . These pre-tRNAs are like those which accumulate in the yeast mutant ts 136 (rna1) in that they have transcribed intervening sequences . The mutations at los1-1 and rna1 complement and segregate independently of each other . The los1-1 mutation affects the expression of all 8 tyrosine-inserting suppressor loci, but does not seem to affect rRNA or mRNA synthesis.

Antimicrob Agents Chemother, 1980 Mar, 17(3), 443 - 9
Resistance to adriamycin cytotoxicity among respiratory-deficient mutants in yeast; Hixon SC et al.; Saccharomyces cell uptake of Adriamycin and the ensuing cytotoxic response were found to be dependent upon the ionic strength of the medium used for drug treatment . A given concentration of Adriamycin which inhibited growth in complete medium ws found to be significantly cytotoxic when administered in water . Many survivors after Adriamycin treatment in water were found to be respiratory-deficient petite mutants containing mitochondrial deoxyribonucleic acid mutations . Petite mutants arising after Adriamycin treatment were not induced but selected from the preexisting population of spontaneously derived petite mutants (normal frequency, 2%) due to an increased resistance of these mutants to killing by Adriamycin as compared with normal respiratory-sufficient cells . The responses to Adriamycin in mitochondrial deoxyribonucleic acid respiratory-deficient mutants (rho-, rho degrees, mit-) with different impaired mitochondrial functions was studied . All were similarly more resistant to killing by Adriamycin than wild-type cells . The common deficiency shared by these mutants, i.e., nonfunctioning electron transport, may play a role in protecting these mutants from Adriamycin cytotoxicity . In addition, normal cells grown on glycerol, requiring aerobic respiration for carbon source utilization were more susceptible to killing by Adriamycin than cells grown on glucose . These studies suggest that a mitochndrial function in yeast may interact with Adriamycin to potentiate a cell cytotoxic mechanism of the drug.

Arch Dis Child, 1980 Mar, 55(3), 189 - 93
Yeast opsonisation in children with chronic diarrhoeal states; Candy DC et al.; Four patients with defective yeast opsonisation and protracted diarrhoea are reported . Plasma infusions improved the opsonising function in all 4 and the diarrhoea in 3 . This immunological abnormality was assessed in 100 sequential patients with chronic diarrhoea associated with various gastrointestinal disorders; 52 with protracted diarrhoea and failure to thrive of undetermined cause, 26 with 'toddler diarrhoea', 8 with coeliac disease, 5 with chronic inflammatory bowel disease, and 9 with miscellaneous disorders . 23% of the patients with protracted diarrhoea of undetermined cause had defective opsonisation, a greater proportion (P less than 0.05) than that in 'toddler diarrhoea' or the remaining patients, in whom the frequency (4%) was similar to that (5%) in healthy populations . We suggest that yeast opsonisation be tested in children with protracted diarrhoea, as plasma infusions can be an effective form of treatment.

Proc Natl Acad Sci U S A, 1980 Mar, 77(3), 1417 - 21
Processing of precursors of 21S ribosomal RNA from yeast mitochondria; Merten S et al.; The transcription and processing of mitochondrial 21S rRNA in a petite strain of Saccharomyces cerevisiae has been examined by electron microscopic analysis of R-loop hybrids and by hybridization of labeled mitochondrial DNA probes to RNA transferred to diazobenzyloxymethyl paper . We have shown the presence of a large {5.1- to 5.4-kilobase (kb)} transcript that appears to be a precursor of mitochondrial 21S rRNA . This transcript contains sequences homologous to those of the mature 21S rRNA, to the intervening sequence present in the gene, and to additional sequences at the 3' end of the molecule . Our data suggest that this precursor of 21S rRNA is processed in two steps . The intron sequence is usually excised first, followed by removal of the extra 3' sequences . In some cases, however, the 3' extension is first removed and the intron sequence is then excised . Both pathways appear to lead to formation of the 3.1-kb mature 21S rRNA and a stable 1.2-kb intron transcript . Similar results were obtained with grande MH41-7B mitochondrial RNA by RNA transfer hybridization . We have also observed a number of additional transcripts that may be normal processing intermediates or may result from faulty cleavage-ligation during excision of the intervening sequence.

Eur J Biochem, 1980 Mar, 105(1), 75 - 80
Small-size mRNAs code for ribosomal proteins in yeast; Bollen GH et al.; In order to identify and to study the ribosomal protein genes in yeast we have tried to purify the mRNA coding for ribosomal proteins . Poly(A)-containing RNA from the yeast Saccharomyces carlsbergensis was fractionated according to size using preparative sucrose gradient centrifugation . The various (size) fractions were translated in vitro in a wheat germ cell-free system . The products were analysed by sodium dodecylsulfate/polyacrylamide gradient gel electrophoresis as well as by acetic acid/urea gel electrophoresis . It was found that an mRNA fraction of about 9 S directs the synthesis in vitro of proteins that have properties characteristic of ribosomal proteins, i.e . they are both small and basic . The ribosomal nature of these proteins was further established by two-dimensional gel electrophoresis . This small-size mRNA fraction can be used as a probe for the identification of ribosomal protein genes in recombinant DNA molecules.

Can J Biochem, 1980 Mar, 58(3), 194 - 200
Comparative studies of kinetic and optical properties of rabbit muscle, sturgeon muscle, and yeast pyruvate kinase; Kwan CY et al.; The kinetic and optical properties of pyruvate kinase isolated from rabbit muscle, sturgeon muscle, and yeast were compared using various activating divalent metal ions as probes for functional features and using ultraviolet circular dichroism (cd) measurements for conformational features, respectively . All three preparations of pyruvate kinase were similar in many aspects, such as activating efficiencies of the four activating metal ions, Mg(II), Co(II), Mn(II), and Ni(II) and pH-rate profiles, suggesting the presence of a similar metal binding locus of these enzymes as well as a common underlying mechanism of action . L-Phe inhibited the rabbit muscle enzyme and turned the hyperbolic kinetics into a sigmoidal kinetic with respect to phosphoenolpyruvate at alkaline pH, while fructose-1,6-biphosphate activated the sturgeon muscle and yeast enzymes and turned the sigmoidal kinetics into hyperbolic kinetics with respect to phosphoenolpyruvate . The ultraviolet cd spectral changes qualitatively correlated well with kinetic observations of all three native enzymes in the presence and absence of allosteric effectors . Our results suggested that there are at least two conformational states of pyruvate kinase which are inducible by the binding of substrate and (or) allosteric effectors . The conformational changes from one form to another in these enzymes are very similar, especially between the rabbit and sturgeon muscle enzymes.

Mutat Res, 1980 Mar, 70(1), 37 - 48
Genetic analysis of gamma-ray mutagenesis in yeast . III . Double-mutant strains; McKee RH et al.; Comparisons between the 60Co gamma-ray survival curves of diploid strains of the yeast Saccharomyces cerevisiae that are homozygous for two non-allelic radiation-sensitive mutations and the corresponding single-mutant diploids suggest that there are two main types of repair of ionizing radiation damage in this organism . The first, which is defined by the rad52 epistasis group, depends on the activities of the RAD50 through RAD57 genes and is responsible for repairing the larger amount of lethal damage . Previous work {22} shows that this type of repair is essentially error-free . The second, defined by the rad6 epistasis group, depends on the activities of the RAD6, RAD9, RAD18, REV1 and REV3 genes and repairs a smaller, though still substantial, amount of lethal damage . It is also responsible for induced mutagenesis {22, 23} . Data for survival and mutation induction after irradiation in air and partial anoxia show that oxygen-dependent damage can be repaired by either of these two pathways . They also show similar oxygen-enhancement ratios for survival and mutagenesis.

Mutat Res, 1980 Mar, 70(1), 29 - 35
Biochemical analysis of damage induced in yeast by formaldehyde; Magana-Schwencke N et al.; Cross-links between DNA and proteins were induced by formaldehyde treatment in yeast cells . This damage can be repaired by post-treatment incubation of cells or protoplasts in nutrient medium . This repair was observed for wild-type cells as well as for a UV-sensitive, excision-deficient mutant (rad1-3), also sensitive to the lethal effect of formaldehyde.

Cell, 1980 Mar, 19(3), 765 - 74
Unequal meiotic recombination within tandem arrays of yeast ribosomal DNA genes; Petes TD; Recombinant DNA procedures and the yeast transformation technique were used to insert the yeast gene LEU 2 (coding for beta-isopropylmalate dehydrogenase) into the tandem array of ribosomal DNA genes of the yeast Saccharomyces cerevisiae . These insertions were shown by genetic and physical techniques to be unstable in meiosis . The meiotic instability was found to be the result of a high level of unequal recombination between ribosomal DNA gene clusters located on sister chromatids.

Cell, 1980 Mar, 19(3), 753 - 64
The structure of transposable yeast mating type loci; Nasmyth KA et al.; A recombinant plasmid containing a MAT alpha mating type locus of Saccharomyces cerevisiae has been isolated by its ability to complement a sterile mat alpha mutation . The plasmid hybridizes to restriction fragments containing both active mating type loci (MATa and MAT alpha) and both silent mating type loci (HMRa and HML alpha) . All loci therefore have common sequences . Recombinant lambda clones of the locihave been isolated by plaque hybridization and their structures have been compared by a heteroduplex analysis . At its center, each locus contains one of two apparently nonhomologous sequences . Loci concerned with the alpha phenotype (MAT alpha and HML alpha) contain and 850 bp alpha-specific sequence, whereas loci concerned with the a phenotype (MATa and HMRa) contain a 700 bp a-specific sequence . The a- or alpha-specific sequences are surrounded by DNA sequences that are common to all loci . These homologous sequences extend for 230 bp on the left and 700 bp on the right . They appear to be unrelated to each other . Surprisingly, HML alpha and HMRa differ in their extent of homology to MATa and MAT alpha outside the above regions . HMRa lacks an extensive (700 bp) DNA sequence to the right of the large right-hand homologous region, and possibly also a small (90 bp) sequence to the left of the small left-hand homologous region, both of which are present at HML alpha, MATa and MAT alpha . Hybridization studies have shown that the 700 bp sequence is present at HMLa but absent at HMR alpha alleles . It is therefore characteristic of HML, irrespective of whether it contains a- or alpha-specific sequences . The results imply that mating type interconversion is effected by transposition of DNA sequences from HML or HMR to MAT, as predicted by the controlling element model of Oshima and Takano (1971) and the Cassette model of Hicks, Strathern and Herskowitz (1977).

Biochim Biophys Acta, 1980 Feb 14, 611(2), 323 - 32
Purificaton and characterization of S-formylglutathione hydrolase from a methanol-utilizing yeast, Kloeckera sp . No . 2201; Kato N et al.; S-Fromylglutathione hydrolase (EC 3.1.2.12), a glutathione thiol esterase, was purified from a methanol-utilizing yeast, Kloeckera sp . No . 2201, to homogeneity as judged by polyacrylamide gel electrophoresis . The molecular weight of the native enzyme was determined to be 58 000 by gel filtration . The enzyme appeared to be composed of two identical subunits (Mr = 31 000) . The apparent Km for S-formylglutathione was 0.077 mM . The optimum temperature was 50 degrees C and the optimum pH was 6.4-6.6 . The enzyme was inhibited by several types of sulfhydryl reagents . The purified enzyme preparation contained no activity of formaldehyde dehydrogenase or of formate dehydrogenase . It is thought that three enzymes, formaldehyde dehydrogenase, S-formylglutathione hydrolase and formate dehydrogenase, participate in the oxidation of formaldehyde to CO2 in Kloeckera sp . No . 2201.

J Biol Chem, 1980 Feb 10, 255(3), 888 - 94
Biosynthesis of the yeast cell wall . I . Preparation and properties of beta-(1 leads to 3)glucan synthetase; Shematek EM et al.; The synthesis of the major linkage found in yeast cell wall structural polysaccharides, glucosyl-beta-(1 leads to 3)-glucosyl, was studied with a membrane preparation from Saccharomyces cerevisiae . The sugar donor was UDP-glucose, and the reaction required addition of glycerol bovine serum albumin, and ATP or GTP for maximal activity . Under optimal conditions, extremely efficient glucose transfer was obtained, with 20 to 50% of the substrate utilized in 20 min at 30 degrees C . The polysaccharide formed in the reaction was insoluble in water and soluble in alkali; it was characterized enzymatically and chemically as a beta-(1 leads to 3)-linked linear glucan of chain length 60 to 80 . The terminal reducing group was found to be labeled with 14C, as was the substrate used; therefore, the polysaccharide is synthesized de novo . For each glucosyl group transferred, one equivalent of UDP was formed . No evidence was found for a lipid-linked intermediate . When yeast protoplast lysates were subjected to fractionation by centrifugation in Renografin gradients, glucan synthetase was found in the plasma membrane fraction, with the same distribution and sidedness as chitin synthetase . Because of the spatially restricted growth of the cell wall during cell division in budding yeasts, this result suggests localized and reversible activation of the enzyme during the cell cycle.

Poult Sci, 1980 Feb, 59(2), 459 - 67
Effects of additional vitamins, minerals, or brewer's yeast upon leg weaknesses in broiler chickens; Plavnik I et al.; Leg weaknesses occurring in commercial broiler chickens were studied in three experiments . No significant improvement was obtained by added dietary levels of known anti-perotic factors . Definite improvements in leg weaknesses occurred when the complete, practical diet was supplemented with 2.5 and 5.0% brewer's dried yeast.

J Bacteriol, 1980 Feb, 141(2), 981 - 4
Induction of synchronous growth in the yeast phase of Wangiella dermatitidis; Roberts RL et al.; Synchronous yeast-phase cultures of Wangiella dermatitidis were induced by starvation, heat shock, and inhibition of deoxyribonucleic acid synthesis by hydroxyurea . Hydroxyurea-induced synchrony resulted in some distortion of the yeast-phase cell cycle . However, induction of synchrony by hydroxyurea is a rapid and simple technique which generates a marked degree of synchronous growth.

Biokhimiia, 1980 Feb, 45(2), 355 - 62
{Mitochondrial proteinase of yeast splitting the products of mitochondrial translation}; Kal'nov SL et al.; It has been shown that mitochondria of the yeast Saccharomyces cerevisiae contain proteinase, which is bound to the inner mitochondrial membrane and catalyzes the hydrolysis of mitochondrial translation products in vitro . The efficiency of proteolysis depends on the state of mitochondria: e.g . the degradation of completely formed organelles corresponding to stationary cells, is twice as low as compared to the "young" organelles typical for the beginning of a logarithmic phase of growth . The proteolysis of mitochondrial translation products can occur not only in mitochondria, but also in "inside out" submitochondrial particles . In order to prove the absence of concomitant vacuolar proteinases in preparations of mitochondria and submitochondrial particles, the specific antisera against proteinases A and B have been used . The activity of mitochondrial proteinase is completely inhibited by the natural peptide inhibitors antipain and chymostatin . Of special importance is the fact that another natural peptide inhibitor--leupeptin, having no effect on the activities of vacuolar proteinases, significantly decreases the rate of hydrolysis of mitochondrial translation products . The role of yeast mitochondrial proteinase in regulation of mitochondrial formation is discussed.

Mol Gen Genet, 1980 Feb, 177(3), 375 - 87
Mutations within an intron and its flanking sites: patterns of novel polypeptides generated by mutants in one segment of the cob-box region of yeast mitochondrial DNA; Claisse ML et al.; We have undertaken a systematic examination of the polypeptides accumulating in thirteen (out of 23) mutants in the intron cluster box7 and its flanking clusters box2 and box9 of the cob-box (cytochrome b) region of the mitochondrial genome of Saccharomyces cerevisiae . We have subjected these polypeptides to fingerprint analysis, both sequential and in parallel, with two proteases in order to disclose sequence homologies and differences between the different novel polypeptides themselves, and between them and the wild type product of the gene, i.e . apocytochrome b . One of our aims has been to establish the existence of possible correlations between the nature of the novel polypeptides and the fine structure genetic map of that segment of the mitochondrial genome . Our results show that all box7 mutants accumulate the following set of polypeptides not seen in wild type cells: a) a characteristic set of "large" polypeptides consisting of three species: p56, p42 and p35 or p34.5; b) a polypeptides p23; c) a much shorter fragment (of which the apparent molecular weight varies from 12.5 to 13, according to the mutation) with the exception of two mutants; d) in addition, the majority accumulate in varying amounts a polypeptide p30 closely related to but not identical with apocytochrome b . Moreover only two box7 mutants accumulate a polypeptide in the range of mobilities corresponding to 25-27 Kd (referred to as class p26) while such a polypeptide is seen in all box9 and box2 mutants examined with one exception in box2.

J Bacteriol, 1980 Feb, 141(2), 558 - 64
Yeast mutants auxotrophic for choline or ethanolamine; Atkinson KD et al.; Three mutants of the yeast Saccharomyces cerevisiae which require exogenous ethanolamine or choline were isolated . The mutants map to a single locus (cho1) on chromosome V . The lipid composition suggests that cho1 mutants do not synthesize phosphatidylserine under any growth conditions . If phosphatidylethanolamine or phosphatidylcholine, which are usually derived from phosphatidylserine, were synthesized from exogenous ethanolamine or choline, the mutants grew and divided relatively normally . However, mitochondrial abnormalities were evident even when ethanolamine and choline were supplied . Diploids homozygous for the cho1 mutation were defective in sporulation . Growth on nonfermentable carbon sources was slow, and a high proportion of respiratory-deficient (petite) cells were generated in cho1 cultures.

Clin Biochem, 1980 Feb, 13(1), 41 - 5
Production of low glucose serum for quality control and evaluation of yeast treatment, lyophilization and storage conditions on serum constituents; Pelletier O et al.; In order to provide quality control serum in the hypoglycemic range, pooled human serum was treated with yeast . Yeast destroyed about 50% of the serum glucose in about 4 1/2 hrs . The yeast-treated serum remained suitable for quality control of the most commonly analyzed clinical chemistry constituents which showed only very little change in most cases . Serum triglycerides were increased by about 40% and bilirubin decreased by about 20% during the treatment . Lyophilization of serum samples (yeast-treated or not) resulted in significant decreases of some enzymes activities . Exposure at 22 degrees C of samples lyophilized (7 days) and non-lyophilized (4 days) resulted in practically no change except for certain enzymes . No significant differences were observed in the clinical chemistry measurements including glucose one month and three months after preparation of samples lyophilized (stored in a refrigerator) and non-lyophilized (store in a freezer).

Cell, 1980 Feb, 19(2), 313 - 9
Some yeast mitochondrial RNAs are circular; Arnberg AC et al.; 11S and 18S fractions of yeast mitochondrial RNAs, isolated by electrophoresis through agarose gels, have been found by electron microscopy to contain approximately 50% circular molecules . Circles in the 11S fraction have a contour length of 0.36 +/- 0.02 micron, which is approximately equal to the length of the majority of linear molecules also present . Circles in the 18S fraction have an average length of 0.78 +/- 0.11 micron . The size distribution is broader than for the 11S fraction, and we cannot exclude the possibility that more than one size class may be present . The 11S circular RNA forms circular R loops and RNA-DNA hybrids with DNA fragments of the oxi 3 region of mtDNA, which contains the structural gene for subunit 1 of cytochrome oxidase . As judged from the electron micrographs, the complete RNA participates in hybrid formation and the sequences coding for it appear to be continuous . Both 11S and 18S circles withstand treatment with DNAase and pronase . They are not eliminated by treatment with 1 M glyoxal in 50% formamide for 1 hr at 50 degrees C . We conclude that they are covalently closed . The function of the circular RNAs is unknown . They may be active as mRNAs, storage forms, or arise in a cut-and-splice process which generates mRNAs from longer transcripts.

Eur J Biochem, 1980 Feb, 103(3), 471 - 80
Assembly of mitochondria in yeast . Complementation of mitochondrial and cytosolic products in a temporal sequence in vitro; Chandrasekaran K et al.; 1 . Sequential transfer of derepressing yeast spheroplasts from a medium containing chloramphenicol to one containing cycloheximide or vice versa, shows that the cytosolically and mitochondrially synthesized products are synthesized independent of each other and accumulate in the absence of their counterparts . 2 . This has been demonstrated by immunoprecipitation using specific antisera for cytochrome oxidase and ATPase enzymes . 3 . The independently accumulated products have been shown to complement each other for the expression of enzyme activity, upon mixing in vitro . 4 . By varying the time of treatment with cycloheximide, thereby allowing the mitochondrial protein synthesis to proceed to different extent, a time sequence in the appearance of the mitochondrially synthesized products is demonstrated.

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