Yeasts

Infect Immun, 1977 Mar, 15(3), 789 - 95
Adoptive transfer of immunity from mice immunized with ribosomes or live yeast cells of Histoplasma capsulatum; Tewari RP et al.; This investigation was designed to compare the role of lymphoid cells and immune serum in protective immunity induced by immunization with ribosomes or live yeast cells of Histoplasma capsulatum . Spleen cells, peritoneal cells, and serum from C3H mice immunized with Histoplasma ribosomes or live cells were transferred intravenously to separate groups of syngeneic recipients . All recipients along with a set of immunized and control mice were challenged intravenously with 4 x 10(6) yeast cells of H . capsulatum, and protection was assessed . Immunization with ribosomes or live cells provided 90 to 100% protection . Mice receiving filtered spleen cells or peritoneal cells from donors immunnized with live cells showed 90 to 100% protection; 80 to 90% protection was observed for mice receiving cells from ribosome-immunized donors . In contrast, no evidence of protection was seen in mice receiving serum from either live-cell- or ribosome-immunized mice . Peritoneal cells were far more efficient than spleen cells in adoptive transfer of immunity . The adoptive immunity in recipients persisted for at least 3 weeks after transfer, the longest period tested in the present study . These results indicate that the immunity elicited by immunization with Histoplasma ribosomes or live cells is mediated by a cellular mechanism.

Biometrics, 1977 Mar, 33(1), 113 - 20
Fitting a model to the growth of yeast colonies; Gani J et al.; When yeast cells reproduce, scars are left on the parent cell where the offspring has budded . Using a branching process model, it is possible to obtain the expectations of numbers of cells with 0, 1, 2, .. . offspring . In this paper, theoretical results are tested against empirical data for three types of yeast cells . We examine the hypothesis that birth and death rates of cells with no previus offspring may differ from those of cells with one or more offspring . It is suggested that the oscillatory empricial results for the proportions of cells with 0, 1, 2, 3 and 4 offspring may be due to different mean budding times for these cells.

Eur J Biochem, 1977 Mar 1, 73(2), 553 - 6
Studies on a carboxypeptidase Y mutant of yeast and evidence for a second carboxypeptidase Activity; Wolf DH et al.; Immunological studies on the carboxypeptidase Y mutant prcl-l of Saccharomyces cerevisiae revealed the origin of mutation in the structural gene of carboxypeptidase Y . The absence of carboxypeptidase Y has no effect on growth, even after drastic changes of growth conditions . A double mutant (prc 1- leu2-) lacking carboxypeptidase Y and auxotrophic for leucine is able to grow on the peptide benzyloxycarbonylglycylleucine (Cbz-Gly-Leu) as sole nitrogen source, indicating the existence of a second carboxypeptidase . Using a new peptidase test, the existence of this second enzyme, called carboxypeptidase S, was confirmed biochemically.

Cell, 1977 Mar, 10(3), 453 - 62
Number and distribution of polyadenylated RNA sequences in yeast; Hereford LM et al.; The poly(A)-containing RNA, isolated from the budding yeast Saccharomyces cerevisiae, has been characterized with regard to the number and distribution of sequences by a kinetic analysis of RNA-cDNA hybridization . In agreement with results previously obtained on metazoan eucaryotes (Bishop et al., 1974), discrete complexity classes were observed . There exist low, medium, and high complexity classes which contain approximately 20, 400, and 2400 sequences, respectively . This measurements of the number of sequences has been verified by hybridization with single copy DNA . 20% of the single copy fraction of the yeast genome is rendered double-stranded by poly(A)-containing RNA . Assuming asymmetric transcription, this is equivalent to approximately 4000 poly(A)-containing sequences, verifying the results obtained with RNA-cDNA hybridization . In addition, the first-order kinetics of the hybridization with single copy DNA verified the notion that most of the sequence complexity is present at the same intracellular concentration . The same number and distribution of sequences were found in poly(A)-containing polysomal RNA and in total RNA, suggesting that most or all of the sequence complexity is on polysomes and is adenylated . The results indicate that RNA-cDNA hybridization is an accurate method for determining sequence complexity values and that yeast, grown under vegetative conditions, has 3000-4000 different mRNA sequences.

Biophys J, 1977 Mar, 17(3), 205 - 12
Inositol-less death in yeast results in a simultaneous increase in intracellular viscosity; Keith AD et al.; Inositol auxotrophs of yeast developing on isositol-deficient medium continue protein synthesis for 4-6 h, lose viability rapidly after 6 h, and show an increase in cytoplasmic viscosity as measured by spin label rotational motion . Cycloheximide prevents the rapid loss of cell viability, stops protein synthesis, and simultaneously prevents an increase in cytoplasmic viscosity . From these observations, we infer that intracellular translational diffusion is upset as a consequence of inositol starvation . Cell death may be caused by a modified intracellular diffusion environment.

Biotechnol Bioeng, 1977 Mar, 19(3), 365 - 75
Characteristics of yeast invertase immobilized on porous cellulose beads; Dickensheets PA et al.; Invertase from Candida utilis was immobilized on porous cellulose beads by an ionic-quanidino bond . The immobilized invertase showed optimum activity between pH 4.0 and 5.4, while the free enzyme had a sharp optimum at pH 4.1 . Both temperature profiles were fairly similar up to 55 degrees C . However, above this temperature the immobilized enzyme was more stable than the free enzyme . From the temperature data, the activation energies were found to be 7,322 and 4,052 cal/g mol for the free and the immobilized enzyme, respectively . Candida invertase shows characteristics of substrate inhibition . Both the Km and Ki for the free and the immobilized enzymes were determined . The apparent Ki for the immobilized invertase was much higher than the Ki of the free enzyme, suggesting a diffusion effect . Immobilized invertase molecules deep in the pores only see sucrose concentrations much less than the bulk concentrations . Immobilization, thus, offers certain processing advantages in this regard.

J Biol Chem, 1977 Feb 25, 252(4), 1471 - 5
Dissimilarity in protein chain elongation factor requirements between yeast and rat liver ribosomes; Skogerson L et al.; Factor requirements for yeast and rat liver ribosomes were determined in several different reactions using either yeast or liver factors . In polymerization assays yeast ribosomes required a factor in addition to elongation factor 1 (EF-1) and elongation factor 2 (EP-2) . The third factor (EF-3) requirement was observed with EFs from either yeast or liver for both poly(U)-directed polyphenylalanine synthesis and elongation of endogenous peptidyl-tRNA . No significant effect of EF-3 was observed with liver risomes in either assay . In contrast to results with polypeptide synthesis EF-3 was not required for EF-1 dependent binding of {3H}Phe-tRNA or the translocation-dependent formation of N-acetylphenylalanylpuromycin . Up to 2-fold stimulation of the binding reaction was observed with saturating levels of either yeast or liver EF-1 . No effect of EF-3 was observed on ribosome-EF-2-GDP-fusidic acid complex formation . The data suggest that the yeast EF-3 may be a loosely bound ribosomal protein which is not required for a specific step in the elongation cycle but is involved in the coordination of the partial reactions required for polymerization.

J Biol Chem, 1977 Feb 25, 252(4), 1344 - 9
Noncoordinated transcription in the absence of protein synthesis in yeast; Shulman RW et al.; In the yeast Saccharomyces cerevisiae we have carried out a detailed study of the response of transcription to the inhibition of translation . Measurement of the incorporation of labeled bases and nucleosides into the nucleoside triphosphate pools revealed that amino acid deprivation brings about a 10- to 50-fold inhibition of such labeling . Therefore accurate comparisons of RNA synthesis using such precursors are difficult to obtain . To overcome this problem we have turned to the use of L-{methyl-3H} methionine as a precursor, because the labeling of the S-adenosylmethionine pool is relatively unaffected by the rate of protein synthesis . Using this precursor, we have observed that in the absence of protein synthesis the transcription of ribosomal RNA is reduced by 80%, the transcription of messenger RNA is reduced by about 25%, and the transcription of transfer RNA is reduced by less than 20% . These results are obtained when protein synthesis is inhibited either by deprivation of an amino acid or by the addition of cycloheximide . Ribosomal precursor RNA synthesized in the absence of protein synthesis is fully methylated . We conclude that the transcription of rRNA is the primary target of stringent control . Furthermore the inhibition of protein synthesis, itself, may be the trigger for this response.

Eur J Biochem, 1977 Feb 15, 73(1), 131 - 40
Structural studies of yeast flavocytochrome b2: cooperative roles of the alpha and beta globules in the formation of the flavin-binding sites; Mevel-Ninio M et al.; The purpose of the study reported here was the localization of the heme binding sites on the two globular fragments, alpha and beta, of the 'cleaved' form of the flavocytochrome b2 chain . These fragments were partially resolved by means of molecular sieving under denaturing conditions (3 M or 6 M guanidine in the presence of 2-mercaptoethanol) . They were then renatured in the presence of excesses of FMN and protoheme . The protoheme was found to be quantitatively bound to the alpha subunit, confirming previous findings . The flavin binds neither to alpha alone nor to beta alone, but only to the reassociated alphabeta protomer . the results are discussed in terms of the possible occurrence of gene fusion in the formation of the complex flavocytochrome chain of this very particular L-lactate cytochrome c reductase found specifically in yeasts.

Mol Gen Genet, 1977 Feb 15, 150(3), 265 - 70
The extrachromosomal control of nonsense suppression in yeast: an analysis of the elimination of {psi+} in the presence of a nuclear gene PNM; McCready SJ et al.; When a {psi-} strain of yeast mutates to {psi+}, the efficiency of suppression by certain ochre suppressors is increased . The {psi+} phenotype is inherited extrachromosomally . There is a nuclear gene, PNM, which, when mutant, causes loss of the {psi+} phenotype . PNM- is dominant to PNM+ and a heterozygous diploid gradually loses the ability over successive generations, to produce PNM+ {psi+} spores . This paper describes the kinetics of this elimination and the data obtained are discussed in relation to two models of the molecular nature of the {psi} genetic determinant--one considering the {psi} determinant as an autonomous nucleic acid, the other treating the possibility that the {psi} nucleic acid is that which codes for rRNA in the nuclear genome.

Eur J Biochem, 1977 Feb 15, 73(1), 7 - 15
Non-equivalence of the sites of yeast phenylalanyl-tRNA synthetase during catalysis; Fasiolo F et al.; Yeast phenylalanyl-tRNA synthetase, an enzyme with an alpha2beta2 structure, has two active sites for phenylalanine, tRNAphe, phenylalanyladenylate and phenylalanyl-tRNAphe . Determination of phenylalanine binding properties to the free enzyme by equilibrium dialysis shows that only one mole of amino acid binds per mole of enzyme, i.e . absolute negative cooperativity . Binding of the amino acid in the presence of tRNA or of ATP and PPi unmasks the second phenylalanine binding site . The difference between the affinities at the tight and loose binding sites under such conditions is about 10--15 . Titration of phenylalanyladenylate sites by the burst of ATP consumption shows the formation of a (enzyme-phenylalanyladenylate)2 complex in the presence of pyrophosphatase; however, the two sites differ widely in their affinity as shown by dialysis experiments . Measurements of hydrolysis rates of enzyme-bound phenylalanyladenylate suggests that when only the high-affinity adenylate site is occupied, the other protomer can still bind phenylalanine and ATP (in the presence of phenylalanine) . Two moles of Phe-tRNAphe bind to the enzyme with a very high affinity (Kd less than 48 nM) . The presence of millimolar concentrations of ATP, phenylalanine and pyrophosphate triggers negative cooperativity and under these conditions only one mole of Phe-tRNAphe is bound per mole of enzyme with a Kd value of 0.15 muM . The present results give support to interprotomer catalytic cooperativity in the mechanism of action of yeast phenylalanyl-tRNA synthetase.

J Biol Chem, 1977 Feb 10, 252(3), 919 - 26
Steady state kinetics and binding of eukaryotic cytochromes c with yeast cytochrome c peroxidase; Kang CH et al.; 1 . The steady state kinetics for the oxidation of ferrocytochrome c by yeast cytochrome c peroxidase are biphasic under most conditions . The same biphasic kinetics were observed for yeast iso-1, yeast iso-2, horse, tuna, and cicada cytochromes c . On changing ionic strength, buffer anions, and pH, the apparent Km values for the initial phase (Km1) varied relatively little while the corresponding apparent maximal velocities varied over a much larger range . 2 . The highest apparent Vmax1 for horse cytochrome c is attained at relatively low pH (congruent to 6.0) and low ionic strength (congruent to 0.05), while maximal activity for the yeast protein is at higher pH (congruent to 7.0) and higher ionic strength (congruent to 0.2), with some variations depending on the nature of the buffering ions . 3 . Direct binding studies showed that cytochrome c binds to two sites on the peroxidase, under conditions that give biphasic kinetics . Under those ionic conditions that yield monophasic kinetics, binding occurred at only one site . At the optimal buffer concentrations for both yeast and horse cytochromes c, the KD1 and KD2 values approximate the Km1 and Km2 values . At ionic strengths below optimal, binding becomes too strong and above optimal, too weak . 4 . Under ionic conditions that are optimal and give monophasic kinetics with horse cytochrome c but are suboptimal for the yeast protein, yeast cytochrome c strongly inhibits the reaction of horse cytochrome c with peroxidase, uncompetitively at one site and competitively at a second site . The appearance of the second site under monophasic conditions is interpreted as an allosteric effect of the inhibitor binding to the first site . 5 . The simplest model accounting for these observations postulates two kinetically active sites on each molecule of peroxidase, a high affinity and a low affinity site, that may correspond to the free radical and the heme iron (IV) of the oxidized enzyme, respectively . Both oxidizing equivalents may be discharged at either site . Furthermore, the enzyme appears to exist as an equilibrium mixture of a high ionic strength form, EH and a low ionic strength form, EL, the former reacting optimally with yeast cytochrome c, and the latter with horse cytochrome c.

Biochemistry, 1977 Feb 8, 16(3), 436 - 45
Energetics of the cooperative and noncooperative binding of nicotinamide adenine dinucleotide to yeast glyceraldehyde-3-phosphate dehydrogenase at pH 6.5 and pH 8.5 . Equilibrium and calorimetric analysis over a range of temperature; Niekamp CW et al.; The binding of nicotinamide adenine dinucleotide (NAD+) to yeast glyceraldehyde-3-phosphate dehydrogenase (GPDH) has been studied at pH 6.5 and 8.5, at 5,25, and 40 degrees C, by calorimetry, fluorometry, spectrophotometry, equilibrium dialysis, and flow dialysis . As reported earlier for pH 7.3 (Velick S.F., Baggott, J.P., and Sturtevant, J.M . (1971), Biochemistry 10, 779), the binding is accompanied by enthalpy changes which become rapidly more negative as the temperature increases, with delta Cp = -500 to -750 cal deg-1 (mole of NAD+ bound)-1, and by entropy changes which also, as required by the large negative delta Cp, become rapidly more negative with increasing temperature . The binding data at pH 6.5 can be fitted on the basis of either four identical noninteracting sites, or of four sites showing a small degree of negative cooperativity . The data at pH 8.5, particularly at 40 degrees C, require the introduction of positive cooperativity, as was previously shown by Kirschner et al . (Kirschner, K., Eigen, M., Bittman, R., and Voigt, B . (1966), Proc . Natl . Acad . Sci . U.S.A . 56, 1661), and can be equally well fitted on the basis of a sequential model (Adair, G.S . (1925), J . Biol . Chem . 63, 529) or a concerted model (Monod, J., Wyman, J., and Changeux, J.P . (1965), J . Mol . Biol . 12, 88) . It is proposed that the observed thermodynamic changes are largely the result of a hydrophobic effect due to a decrease in the exposure of nonpolar groups to the solvent, and of a tightening of the protein structure when the coenzyme is bound with concomitant decrease in the number of easily excitable internal degrees of freedom.

Biochim Biophys Acta, 1977 Feb 7, 459(2), 290 - 9
Transport of pyruvate and lactate in yeast mitochondria; Briquet M; Evidence for the existence of mediated transport of pyruvate and lactate in isolated mitochondria of Saccharomyces cerevisiae is presented . 1 . The mitochondrial oxidation of pyruvate is specifically inhibited by the monocarboxylic oxoacids alpha-ketoisocaproate and by alpha-cyano-3-hydroxycinnamate, while pyruvate and malate dehydrogenases activities are not inhibited . 2 . The stimulation of the mitochondrial oxidations of succinate, alpha-ketoglutarate and citrate by pyruvate are also inhibited by alpha-cyano-3-hydroxycinnamate . 3 . The {14C}pyruvate uptake by yeast mitochondria follows saturation kinetics and is completely inhibited by alpha-cyano-3-hydroxycinnamate . 4 . Large amplitude passive swellings of mitochondria of the wild type and of cytoplasmic rho- and rho-n mutants are induced by isoosmotic ammonium pyruvate and lactate . These pH-dependent swellings are inhibited by alpha-cyano-3-hydroxycinnamate suggesting that the carrier system is not coded by mitochondrial DNA.

Mol Cell Biochem, 1977 Feb 4, 14(1-3), 87 - 9
Intramitochondrial synthesis of membrane proteins in yeast: differential inhibition by ethidium; Rogers P et al.; Yeast cells (Saccharomyces cerevisiae) were grown in the presence of {14C}phenylalanine and pulse-labelled with {3H}phenylalanine in the presence of cycloheximide . The proteins extractable into chroloform: methanol (2:1) were isolated from mitochondria and analysed by SDS gel filtration . Four protein fractions varying in molecular weight were separated . In order to identify the transcriptional origin and the site of protein synthesis ethidium bromide was used . Different sensitivity of protein syntheses to various concentrations of ethidium was shown . These data are discussed in relation to the possible presence of two classes of membrane-bound polyribosomes in mitochondria.

Mol Cell Biochem, 1977 Feb 4, 14(1-3), 67 - 79
Integration and regulation of mitochondrial assembly in yeast; Mahler HR et al.; The interactions between the mitochondrial and nucleocytoplasmic systems required for mitochondriogenesis have been investigated at several different levels . Those involved in the formation of functional enzyme complexes have been studied using cytochrome oxidase: this multimeric (2 X 7 and 2 X 6 subunits for enzymes from yeast and beef heart respectively) has been resolved, and the mitochondrial contribution has been shown to be dispensible for catalytic function proper . Using novel mutants, with a mitochondrial mode of inheritance, a mitochondrial gene product localized in the oligomycin-sensitive ATPase has been implicated in the assembly not only of this complex, but of cytochrome oxidase as well . Interactions required for the genetic competence of the mitochondrial system have become apparent as a result of studies in the mechanism of action of the highly effective mitochondrial mutagen ethidium bromide . This agent first becomes covalently inserted into mitochondrial DNA and, after its excision, eventually results in extensive degradation of the macromolecule . The excision reaction has now been shown to be performed by a complex between the oligomycin-sensitive ATPase and a DNA-binding protein presumably involved in recognizing the damage . On the level of replication and expression of the mitochondrial genome studies using thermolabile mutants have demonstrated that these processes appear independent of the replication of nuclear DNA but not of its expression.

Appl Environ Microbiol, 1977 Feb, 33(2), 231 - 9
Lipid accumulation in an oleaginous yeast (Candida 107) growing on glucose in single-stage continuous culture; Gill CO et al.; Lipid accumulation of Candida 107, grown at dilution rates from 0.03 to the maximum of 0.21/h, with carbon, nitrogen, phosphate, and magnesium limitations in a chemostat, was maximal at about 40% (wt/wt) with nitrogen-limited medium at a dilution rate of 0.06/h, giving an efficiency of substrate conversion of 22 g of lipid per g of glucose consumed . At higher dilution rates the lipid content decreased . With carbon-limited growth, the highest lipid content (14%, wt/wt) was at the maximum dilution rate . High lipid contents also occurred with phosphate + nitrogen as double limitations of growth, with the lipid content of the yeast (about 35%, wt/wt) continuing to be near maximum at dilution rates also near maximum (0.17/h), thus giving the highest specific rate of lipid formation of any growth conditions (0.59 g of lipid/g of yeast per h) . However, the efficiency of substrate utilization was only 5.2 g of lipid formed per 100 g of glucose consumed . The composition of the fatty acyl residues within the lipid remained constant over many weeks if the steady-state conditions remained unchanged . With carbon-limited growth, the degree of unsaturation of the fatty acids markedly decreased as the dilution rate was increased, but with nitrogen limitation the reverse trend was seen . In all cases, linoleic and oleic acids were the principal fatty acyl residues affected, and their relative proportions always varied in opposite directions . When magnesium was a limiting nutrient, there was a considerable increase in the proportion of myristic acid produced within the lipid . Neutral lipids (predominantly triglycerides) varied from 66 to 92% of the total lipid from carbon- and nitrogen-limited growth; phospholipids (varying from 2 to 25%) were highest in nitrogen-limited growth . The fatty acyl residues within each lipid fraction showed the same variations with changing growth rates.

Genetics, 1977 Feb, 85(2), 225 - 47
Kinetics of mutation induction by ultraviolet light in excision-deficient yeast; Eckardt F et al.; We have measured the frequency of UV-induced reversions (locus plus suppressor) for the ochre alleles ade2-1 and lys2-1 and forward mutations (ade2 adex double auxotrophs) in an excision-deficient strain of Saccharomyces cerevisiae (rad2-20) . For very low UV doses, both mutational systems exhibit linear induction kinetics . However, as the dose increases, a strikingly different response is observed: in the selective reversion system a transition to higher order induction kinetics occurs near 9 ergs/mm2 (25% survival), whereas in the nonselective forward system the mutation frequency passes through a maximum near 14 ergs/mm2 (4.4% survival) and then declines . This contrast in kinetics cannot be explained in any straightforward way by current models of induced mutagenesis, which have been developed primarily on the basis of bacterial data . The bacterial models are designed to accommodate the quadratic induction kinetics that are frequently observed in these systems . We have derived a mathematical expression for mutation frequency that enables us to fit both the forward and reversion data on the assumptions that mutagenesis is basically a "single event" Poisson process, and that mutation and killing are not necessarily independent of one another . In particular, the dose-response relations are consistent with the idea that the sensitivity of the revertants is about 25% less than that of the original cell population, whereas the sensitivity of the forward mutants is about 29% greater than the population average . We argue that this relatively small differential sensitivity of mutant and nonmutant cells is associated with events that take place during mutation expression and clonal growth.

Int J Radiat Biol Relat Stud Phys Chem Med, 1977 Feb, 31(2), 121 - 9
Unscheduled DNA synthesis in diploid yeast after X-irradiation in diffent phases of the cell-cycle; Holtz GW et al.; The uptake of radioactive 5'-dTMP into the DNA of diploid yeast cells was measured in the G1 and S-phase of the cell-cycle . In control cells, the uptake is zero in G1 and increases with time in the S-phase . Cells irradiated in early G1 show an uptake (unscheduled DNA synthesis) which is higher than if irradiation is performed later in G1 . An analysis which takes into consideration the incomplete synchronization of the cell population shows that, at the end of G1, no uptake would be present in an ideally-synchronous population . At the end of G1 the shoulder in the dose-effect curve for cell survival also disappears . This provides additional evidence that the shoulder in a dose-effect curve might be due to repair reactions in living cells.

Int J Radiat Biol Relat Stud Phys Chem Med, 1977 Feb, 31(2), 113 - 9
Photodynamic action of thiopyronine on polyribosomes and cell-free protein synthesis in yeast; Nishiyama-Watanabe S et al.; The treatment of yeast with thiopyronine (TP) caused a degradation of polyribosomes, even if the cells were not illuminated . In contrast, no differences in the polyribosome profiles of illuminated and unilluminated cells could be seen . Likewise, in in vitro experiments, there was no degradation of polyribosomes caused by dark effect or photodynamic action . Cell-free protein synthesis was inhibited up to 75 per cent by the photodynamic effect when the complete system was treated, but only up to 40 per cent when the polyribosomes or enzyme fraction were treated . Since the enzyme fraction contained aminoacyltRNA-synthetases and tRNA, it was necessary to investigate separately the effect of TP on the enzyme and the tTNA . It was shown that the aminoacyl-tRNA-synthetase and not tRNA was effected by the photodynamic action in its biological activity.

J Virol, 1977 Feb, 21(2), 516 - 21
Homology between double-stranded RNA and nuclear DNA of yeast; Vodkin M; The relationship between mycoviral double-stranded (ds) RNA and host cell DNA was investigated . Radiolabeled ds RNA was denatured and reannealed in the presence and absence of denatured DNA . RNA from killer strains of the yeast Saccharomyces cerevisiae and from nonkiller derivatives was utilized . The above-mentioned strains, as well as one that lacks all ds RNA, were sources for extracted DNA . Net hybridization of ds RNA to DNA occurred regardless of the strains from which the respective nucleic acids were prepared.

J Bacteriol, 1977 Feb, 129(2), 640 - 50
Killer toxin for sake yeast: properties and effects of adenosine 5'-diphosphate and calcium ion on killing action; Kotani H et al.; The killer character of strain isolated from the main mash of sake brewing which produces a killer substance for sake yeast was transmitted to hybrids of the strain and a standard strain of Saccharomyces cerevisiae through a cytoplasmic determinant . The character was eliminated at 41 degrees C by incubation followed by growth at 30 degrees C . The killer strain produced the killer toxin in a growth-associated manner . A preparation of crude killer toxin extract showed first-order inactivation and a linear Arrhenius plot between 25 and 40 degrees C, with an activation of energy of 55.0 kcal/mol . Addition of 1% of synthetic polymer protected the toxin from inactivation by agitation but not by heat . Enhancement of the killer action toward sensitive yeast cells by only the nucleotide adenosine 5'-diphosphate (ADP) was observed after plating on agar medium as well as after incubation in liquid medium . The addition of CaCl2 reversed the enhancing effect of ADP on killing activity . This action of CaCl2 was inhibited by cycloheximide, suggesting that protein synthesis is required for recovery of toxin-induced cells in the presence of CaCl2 . Further, CaCl2 overcame the decrease in the intracellular level of adenosine 5'-triphosphate (ATP) enhanced by ADP in killer-treated cells and also inhibited leakage of ATP from the cells with immediate response . The mode of killing action is discussed in terms of a transient state of the cells and the action of ADP and CaCl2.

J Biol Chem, 1977 Jan 25, 252(2), 504 - 7
Purification and properties of acetyl coenzyme A synthetase from bakers' yeast; Frenkel EP et al.; Acetyl-CoA synthetase, utilized in a coupled reaction system, has been shown to be applicable to the spectrophotometric determination of propionic and methylmalonic acids in biological fluids . The isolation of acetyl-CoA synthetase from yeast is simpler than the purification from mammalian sources . This study also presents some properties of the yeast enzyme and compares it to the more extensively studied enzyme isolated from ammmalian tissue . Isolation and purification yielded a preparation with a specific activity of 44 units/mg at 25 degrees . The purified acetyl-CoA synthetase was apparently homogeneous by sodium dodecyl sulfate-poly-acrylamide gel electrophoresis with an estimated subunit molecular weight of 78,000 . Polyacrylamide gel electrophoresis in the presence of ATP revealed a single protein band which contained all of the enzyme activity . Analytical ultra-centrifuge studies indicated the presence of a single protein with a molecular wright of 151,000 and sedimentation velocity analysis revealed a single peak with a sedimentation coefficient of 8.65 So20,w . Similar to the enzyme from mammalian sources, yeast acetyl-CoA synthetase has a high degree of substrate specificity and is active only on acetate and propionate . In addition, the reaction mechanism, as demonstrated by initial velocity patterns obtained from substrate pairs, appeared to be identical to the enzyme from bovine heart . However, the apparent Michaelis constants for the substrates were significantly different from the mammalian enzyme . The yeast-derived enzyme also differed from the mammalian in terms of molecular weight, amino acid composition, pH optimum, effect of monovalent cations, and stability characteristics . Thus, yeast acetyl-CoA synthetase is more easily purified than the mammalian enzyme and provides an excellent preparation for the assay of propionic and methylmalonic acids.

Biochim Biophys Acta, 1977 Jan 24, 496(1), 103 - 14
Effects of glucose and nitrogen source on the levels of proteinases, peptidases, and proteinase inhibitors in yeast; Hansen RJ et al.; In Saccharomyces cerevisiae harvested from early exponential growth on glucose-containing media, the specifc activities of proteinases A and B, carboxypeptidase Y, and the inhibitors IA, IB, IC of these three proteinases, respectively, are found to be 10-30% of the specific activities observed in media without glucose, containing acetate as a carbon source; the activities of two aminopeptidases in glucose-grown cells were 30-50% of those in acetate-grown cells . In contrast to fructose-biphosphatase, phosoenolpyruvate carboxykinase, and cytoplasmic malate dehydrogenase, which are inactivated after the addition of glucose to derepressed cells, the proteinases and inhibitors are not inactivated after glucose addition, but appear to be repressed . Growth of the yeast on poor nitrogen sources or starvation for nitrogen results in 2-3 fold increases in the levels of most proteinases and peptidases, but this effect is not observed with glucose as the carbon source.

Biochim Biophys Acta, 1977 Jan 20, 474(2), 188 - 98
The specificity of the chemical modification of N6-delta 2-(isopentenyl)adenosine in purified yeast tRNA Ser; Horvath P et al.; The specific modification of N6-delta 2-(isopentenyl)adenosine in purified tRNA Ser yeast by mild treatment with KMnO4 and I2 was studied . N6-delta 2-(isopentenyl)adenosine in tRNA SER is specifically modified by iodination, providing us with a suitable method for the quantitative determination of N6-delta 2-(isopentenyl)adenosine in tRNA was found to contain 114 +/- 8 pmol/A260nm unit of N6-delta 2-(isopentenyl)adenosine and gave three labelled fractions on an RPC-5 column . The product obtained after KMnO4 treatment of tRNA Ser was not homogeneous . The enzymatic "reisopentenylation" of KMnO4-treated tRNA Ser resulted in the regeneration of only traces of the original molecule(s) . Most of them had been damaged either by the KMnO4 treatment or in the incubation mixture used for "reisopentenylation".

Biochemistry, 1977 Jan 11, 16(1), 117 - 21
Relaxation spectra of yeast hexokinases . Isomerization of the enzyme; Jentoft JE et al.; Yeast hexokinase isozymes P1 and P11 exhibit a pH dependent, rapid relaxation process at 15 degrees C at enzyme concentrations of 100-474 muM and over a pH range of 6-8 . The process was detected by equilibrium temperature jump spectroscopy using the indicator probe phenol red . The value of 1/tau varies from about 6 ms-1 at pH 8 for both isozymes to 50 ms-1 for P1 and 85 ms-1 for P11 at pH 6 . The data are consistent with a mechanism involving an enzyme isomerization coupled to an ionization . The forward rate constant for the isomerization of the proposed mechanism varies between 3 and 7 ms-1; the ratio of the reverse rate constant to the ionization Ka is between 0.5 and 2 X 10(11) M-1 S-1; the estimated pKa varies between 5.5 and 6.1 . The ranges of values in rate constants and pKa represent variations observed between preparations of the same isozyme and between isozymes . The isomerization rate is at least 50 times faster than catalysis under all conditions and the pKa is lower than that controlling activity . The rate of isomerization is unchanged by addition of sugar and nucleotide ligands, but the amplitude of the process is perturbed . These data imply that isomerizing and ionizing forms are sensitive to events at the active site . These equilibria between forms of hexokinase are fast enough, and have the right properties, to be important to the mechanism and regulation of the enzyme.

Eur J Biochem, 1977 Jan 3, 72(1), 79 - 86
Calorimetric studies on melting of tRNA Phe (yeast); Hinz HJ et al.; The heat effects involved in thermal unfolding of tRNAPhe from yeast have been determined in various buffer systems by direct differential scanning calorimetry . Perfect reversibility of the melting process has been demonstrated for measurements in the absence of Mg2+ ions . The overall molar transition enthalpy, delta Ht = 298 +/- 15 kcal mol-1 (1247 +/- 63 kJ mol-1), has been shown to be independent of the NaCl concentration and the nature of the buffers used in this study . Delta Ht is identical in the presence and in the absence of Mg2+ ions within the margin of experimental error . This experimental result implies a vanishing or very small heat capacity change to be associated with melting . Decomposition of the calorimetrically determined complex transition curves, on the assumption that the experimental melting profile represents the sum of independent two-state transitions, results in five transitions which have been assigned to melting of different structural domains of the tRNA.

Folia Microbiol (Praha), 1977, 22(5), 363 - 72
Transport of ribitol and D-glucose in the yeast Candida guillermondii; Miersch J; The uptakes of the linear polyol ribitol and of D-glucose by Candida guillermondii were found to be carrier-mediated and to require metabolic energy . In glucose-grown cells ribitol possibly enters by simple diffusion but after an induction period a specific transport system is synthesized, inhibitable by higher concentrations of arabinitols, xylitol, mannitol and sorbitol . Actidione blocks the synthesis of the inducible ribitol transport system . Two systems of different affinity for substrate were found to operate in the uptake of both glucose and of ribitol . Counter-transport experiments with ribitol, D-glucose and 3-O-methyl-D-glucose support the carrier nature of the uptake system.

Biochimie, 1977, 59(1), 97 - 104
Lipids of the yeast Hansenula anomala; Ng KH et al.; An analysis of the free lipids of Hansenula anomala was performed . The main fatty acids obtained by saponification of whole cell crude lipids were palmitic, C18:1, C18:2 and C18:3 acids . In mitochondrial lipids the tri-unsaturated acid was present as traces . Fatty acid composition of each class of lipids was also determined . Phosphatidylcholine and phosphatidylethanolamine were the main phospholipids; phosphatidylserine, phosphatidylinositol and cardiolipin were also characterized . The most abundant sterols were ergosterol and lanosterol . An acetate of a 24-ethyl cholesterol was also isolated . Two glycolipids, a galactosyl diglyceride and a glucosyl ceramide were identified; concerning the galactosyl diglyceride, the content of C18:3 acid was higher than in other lipid classes . In the glucosyl ceramide, the main fatty acid was alpha-hydroxy C18:0 acid; C16:0, C18:1, C18:2 and C18:3 acids were present too . The long chain base was shown to be C18-phytosphingosine (4-hydroxy C18 sphinganine) . Some similarities and differences with Saccharomyces cerevisiae are discussed.

Z Allg Mikrobiol, 1977, 17(2), 109 - 15
{Protein crystals and tubuli bundles in yeast cells . VI . Light-and electron microscopy studies as well as biochemical studies on alcohol dehydrogenase activity of isolated crystals}; Kunkel W; Isolated crystals from Saccharomyces carlsbergensis, stabilized by Cd2+ or Zn2+, retain their enzymatic activity as shown by topochemical reactions . During these reactions the crystals disintegrate characteristically . Stages of this disintegration and deposition of reaction products have been demonstrated by light and electron microscopy . Ground plasmatic and mitochondrial alcoholdhydrogenase has been solubilized by means of 0.01 M EDTA from Zn2+ stabilized crystals separated by gel electrophoresis and proved to be active.

Bioinorg Chem, 1977, 7(2), 141 - 50
Multiple roles of metal ions in the reaction catalyzed by yeast inorganic pyrophosphatase; Butler LG et al.; Yeast inorganic pyrophosphatase has three roles for metal ions in its reaction: activator, substrate and structural . Out of a wide variety of metal ions tested, only Mg2+, Zn2+, mn2+ and Co2+ can fulfill both the activator and substrate roles . Several other metal ions inhibit the Mg2+-stimulated activity; the strong inhibition by Ca2+ (and probably Cd2+) is due to interference with both activator and substrate roles, while the weaker inhibition by Sr2+ (and possibly Cu2+ and Ni2+) is due to interference with only the substrate role . Rare earth ions strongly stimulate nonenzymic PPi hydrolysis but do not activate the enzyme . Despite its ability to fulfill both the activator and substrate roles . Zn2+ causes inactivation of the enzyme, probably by interference with the "structural" Mg2+ . The results suggest that the three roles for metal ions are independent (an individual metal ion can satisfy only one at a time) and that the metal ion specificity for the three roles declines in the order: structural greater than substrate greater than activator.

Z Allg Mikrobiol, 1977, 17(5), 353 - 8
{Comparative morphological studies of yeast cells using automated image analysis}; Muhlig P et al.; The ultrastructural alterations in cells of Candida utilis caused by the influence of copper ions have been studied by means of quantitative image analysis . A model has been proposed which presents the following informations: The main effect of the copper ions is represented by an increase of the volume of the whole cell and of that part of the cell which consists of nucleus, vacuoles, and inclusions (particles and globules) . Nevertheless, neither the absolute volume of mitochondria, nor the density of mitochondria are influenced by high concentrations of copper ions in the culture medium.

Antonie Van Leeuwenhoek, 1977, 43(2), 129 - 42
Biosynthesis of the yeast cell wall: selective assays and regulation of some mannosyl transferase activities; Elorza MV et al.; Assays have been developed for some transfer reactions involved in the synthesis of Saccharomyces cerevisiae wall mannoproteins, both in a particulate preparation in the presence of EDTA or Triton X-100, and after lipid extraction with chloroform-methanol at -20 C . The mannosyl transferase activities were also studied in cells made permeable to GDP-mannose by toluene-ethanol treatment ("in situ") . In these permeabilized cells, the glycosylating reactions dependent on lipid carriers (dolichol derivatives) did not function, but those independent of them were unaffected . The lipid-independent mannosyl transferase activities were partially inhibited by nucleotide diphosphates probably in a competitive manner . Increase of the nucleotide diphosphate pool "in vivo" might slow down the speed of the transfer reactions carried out by the mannan synthetase system.

Biochimie, 1977, 59(4), 381 - 91
{Primary structure of tRNA Thr 1a and b from brewer's yeast}; Weissenbach J et al.; One of the two major species of brewer's yeast tRNA threonine (tRNA Thr 1) has been purified by countercurrent distribution followed by two chromatographic steps (respectively on a Sepharose 4B and a BD-cellulose column) . Complete digestion with pancreatic and T1 RNases and a partial hydrolysis with T1 RNase followed by the isolation and determination of the nucleotide sequences of the resulting fragments permitted the derivation of its primary structure . tRNA Thr 1 is in fact a mixture of two subspecies differing only by a A49-U65 base pair in 50 per cent of the molecules which is replaced by a G49-C65 pair in the other 50 per cent . These two subspecies consist of 76 nucleotide residues including 14 minor nucleotides . They show a characteristic m3C at the 3'terminal end of the anticodon loop, an anticodon I-G-U followed by t6A and C48, uncompletely modified (50 per cent) to m5C within the 5 nucleotides long extra-arm . The minor nucleotides m2G m2 2G are located at positions in which they generally occur in the tRNA structures as does m1A within the T-psi-C loop.

Acta Biol Med Ger, 1977, 36(11-12), 1523 - 4
Characterization and function of intracellular proteinases and proteinase inhibitors from yeast; Holzer H; Data on the proteinase inhibitors IA, IB and IC from yeast and their possible intracellular interaction with the proteinases A and B and carboxypeptidase Y are presented . A role of proteolysis in "catabolite inactivation" is discussed.

Acta Biol, 1977, 28(1), 49 - 58
Optical polarization reveals different ultrastructural molecular arrangement of polysaccharides in the yeast cell walls; Fischer J; The topo-optical aldehyde bisulfite-toluidine blue (ABT) reaction of vicinal OH and amino-OH groups offers new ways to study the ultrastructure of polysaccharides in different biological substrates . Through oriented dye binding on the reacting groups, the ABT reaction induces strong birefringence on the linearly ordered polysaccharides, which is negative with respect to their chain length . Using this method, two types of molecular order of the polysaccharides could be distinguished in the cell walls and capsules of yeasts . (1) The optically negative spherulitic character of the yeasts after the ABT reaction indicated that the toluidine blue molecules were bound tangentially (in a surface-parallel pattern) while the polysaccharide chains of the cell walls and capsules were oriented mainly radially . This structural pattern may be explained as resulting from a helicoid conformation of the polysaccharide component . (2) Acid or alkali hydrolysis removed the radially oriented polysaccharide component of the cell wall . The remaining, resistant polysaccharides showed up in the form of optically positive spherulites indicating radially oriented dye molecules on a circularly ordered, micellar polysaccharide texture.

Nucleic Acids Res, 1977, 4(5), 1609 - 31
Complementary addressed modification of yeast tRNA Val 1 with alkylating derivative of d(pC-G)-A . The positions of the alkylated nucleotides and the course of the alkylation in the complex; Grineva NI et al.; Yeast tRNA Val 1 alkylation with 2', 3'-O-4-(N-2-chloroethyl-N-methylamino) benzylidene d(pC-G)-A proceeds at 20 degrees - 30 degrees C in the complementary complexes which are formed by d(pC-G)-A greater than RC1 binding to 3 sequences of tRNA Val 1 : psi-C-G58 in the T loop, C-G40 at the 3'-side of the anticodon loop and C-G18 in the D loop . The reaction in the complexes results in A53, I35, and psi 13 alkylation to form beta-/N-methyl-N-(formylphenyl 17 amino/ethyl-tRNA Val 1 with the relative rate constants of the alkylation that are 3 or 2 orders of magnitude higher than that for the alkylation without a complex formation . It is the third nucleotide from the 5'-terminus of the binding site of the modifying agent that is subjected to alkylation in the t RNA Val 1 . The course of the alkylation does not depend on the possible base pairing of the 3'-terminal nucleotide of the reagent . The extent of the reagent binding and the relative rate constants of the alkalytion in the complexes indicate the following order of the complex stability: (psi-C-G58) greater than (CO-G40) approximately (C-G18) at 20 degrees and (psi-C-G58) greater than (C-G40) greater than (C-G18) at 30 degrees.

Nucleic Acids Res, 1977, 4(5), 1429 - 48
Analysis of chromosomal integration and deletions of yeast plasmids; Cameron JR et al.; Plasmid DNAs from six strains of Saccharomyces cerevisiae were compared . Three different plasmids were found, designated Scp 1, Scp 2 and Scp 3, with monomer lengths of 6.19, 6.06 and 5.97 kilobases as referenced to sequenced phiX174 DNA . DNA from each of the plasmids was inserted into a lambda vector DNA . Hybrid phage containing inserted DNA of the desired size were enriched by genetic selection and their DNAs analysed by rapid techniques . All three plasmids share the same organization, two unique sequences separated by two inverted repeats, and share basically the same DNA sequences . Scp 2 and Scp 3 differ from Scp 1 by missing a unique HpaI site and by having small overlapping deletions in the same region . The HpaI site in Scp 1 is, therefore, in a nonessential region and suitable for insertion of foreign DNA in the potential use of the yeast plasmid as a vector . Hybridization of labelled cloned plasmid DNA to restriction fragments of linear yeast DNA separated on agarose gels showed that the plasmid DNA was not stably integrated into the yeast chromosomal DNA.

Nucleic Acids Res, 1977 Jan, 4(1), 207 - 21
The iminoproton NMR spectrum of yeast tRNA-Phe predicted from crystal coordinates; Geerdes HA et al.; The ring current effects on the base paired iminoprotons in yeast tRNA-Phe have been calculated from crystal coordinates . The results in conjunction with independently determined intrinsic positions of the iminoprotons in various base pairs enable us to predict the low field NMR spectrum of yeast tRNA-Phe . It turns out that the calculated NMR spectra are very sensitive to slight changes in structure . Moreover the crystal and solution structure are identical as far as the present methods go.

Mikrobiologiia, 1977 Jan-Feb, 46(1), 101 - 3
{Study of preliminary irradiation with wave-lengths 366 and 405 nm on lethal UV-damage to yeast cells}; Buturlakin MS; The protective action of irradiation with wavelengths of 366 and 405 nm on the cells of Saccharomyces cerevisiae, XI race, against lethal lesions caused by short-wavelength UV was studied . Among the total number of the cells with lethal lesions caused by UV, 25--30% of the cells were protected by light with the wavelength of 405 nm, and 50--55% of the cells were protected by light with the wavelength of 366 nm . Lethal UV lesions of the cells are supposed to be of different nature.

Biochem J, 1977 Jan 1, 161(1), 181 - 3
The catalytic activity of monomeric yeast hexokinase A; Yip BP et al.; It has been suggested {Williams, D.C . & Jones, J.G . (1976) Biochem . J . 155, 661-667} that monomeric hexokinase isoenzyme A is not catalytically active . We here present data from reacting-enzyme sedimentation, dissociation experiments and from previous studies which are consistent with the monomeric form possessing catalytic activity.

Proc Natl Acad Sci U S A, 1977 Jan, 74(1), 305 - 9
Nonsense suppressors of yeast cause osmotic-sensitive growth; Singh A; Many nonsense suppressors of Saccharomyces cerevisiae cause growth inhibition on hypertonic media . Eight tyrosine-inserting UAA (ochre) suppressors, eight tyrosine-inserting UAG (amber) suppressors, a leucine-inserting UAG suppressor, and a serine-inserting recessive lethal UAG suppressor cause osmotic sensitivity, whereas a serine-inserting UAA suppressor does not cause sensitivity . Although the mechanism is not understood, the growth inhibition of specific suppressors on hypertonic media is correlated with their efficiencies of suppression . This heretofore unknown property of nonsense suppressors is useful for mitotic mapping, selecting tRNA mutants, selecting antisuppressors, and scoring nonsense suppressors.

J Gen Microbiol, 1977 Jan, 98(1), 215 - 21
Synthesis of ribosomal and transfer ribonucleic acids in yeast during a nutritional shift-up; Waldron C; The growth rate of Saccharomyces cerevisiae was increased by adding a mixture of amino acids to cultures containing proline as the sole nitrogen source . The transition from balanced growth in the basal medium (doubling time 4 h) to balanced growth in the enriched medium (doubling time 2 h) took about 2-5 h . The rate of RNA accumulation increased soon after the enrichment to almost its final value . This increase began after a short lag of 10 to 15 min, therefore synthesis of new RNA polymerase molecules may be required before stable RNA production can increase . The different stable RNA species were not stimulated at different times after the enrichment, but all increased continuosly throughout the transition . The rRNA species accumulated in a co-ordinate fashion at a rate faster than the rate of tRNA accumulation.

J Bacteriol, 1977 Jan, 129(1), 472 - 81
Deoxyribonucleic acid sequence organization of a yeast plasmid; Livingston DM et al.; Two-micrometer deoxyribonucleic acid (DNA), a circular plasmid of Saccharomyces cerevisiae, contains two nontandem repeated sequences which are inverted with respect to one another . These repeated sequences together account for 21% of the molecule length . Restriction endonuclease analysis and electron microscopy demonstrated the existence of two forms of 2-mum DNA differing in the orientation of the interstitial segments bounded by the inverted repeated sequences . The two forms of 2-mum DNA could result from an intramolecular reciprocal recombination between inverted repeat elements . A map containing the restriction endonuclease sites and the units of the inverted repeat has been constructed.

Biochimie, 1977, 59(10), 805 - 11
{Inhibition of the yeast respiratory system by Zn-protoporphyrin and effect of photolysis of this substance}; Djavadi FH et al.; We have shown earlier that yeast cells grown in synthetic mediums supplemented with Zn++ accumulate large amounts of Zn-protoporphyrin within their mitochondria . This accumulation is accompanied by an inhibition of respiration (3) . This study deals with the effect of light on the respiratory inhibition and the release of respiratory control which are observed if Zn-protoporphyrin is added to isolated mitochondria which are initially devoid of this pigment . In addition, we have studied the effect of light on the respiratory inhibition exerted by Zn-protoporphyrin accumulated in vivo . The following results were obtained: 1) The light-induced destruction of Zn-protoporphrin which had been added in vitro to Zn-protoporphyrin-free mitochondria significantly inhibits respiration and phosphorylation . Under these conditions, the extent of the inhibitions increases with the concentration of the added Zn-protoporphyrin and the duration of illumination . 2) Accumulation of Zn-protoporphyrin within the cells causes an inhibition of the respiratory activities and the activities of succinate-cytochrome c reductase and NADH-cytochrome c reductase of the mitochondria . Illumination of the isolated mitochondria from Zn-protoporphyrin-containing cells enhances the inhibition of these activities . No light-induced inhibition of these activities is observed with mitochondria from cells devoid of Zn-protoporphyrin.

Z Allg Mikrobiol, 1977, 17(4), 293 - 7
Electron microscopic studies on the formation of vesicular bodies during cell wall degradation and regeneration in yeast; Dmitriev VV et al.; Vesicular bodies are observed during enzymatic degradation of the yeast cell wall and in the course of wall regeneration . In both cases various types of vesicles are formed and exocytated by different mechanisms . They are characterized cytochemically and their possible role in cell wall regeneration is discussed.

Biokhimiia, 1977 Jan, 42(1), 79 - 84
{Interaction of thiamine pyrophosphokinase from brewer's yeast with thiamine and adenosine-5'-triphosphate}; Voskoboev AI et al.; The interaction of thiamine pyrophosphokinase (Thiaminkinase EC 2.7.6.2) with thiamine and ATP was studied . It was shown that the mechanism of the thiaminokinase reactions is Rapid Equilibrium Random Bi -- Bi . The enzyme binds 8 moles ATP and 1 mole thiamine per mole protein Ks = 0,8-10(-3) and 4.10(-6) M for ATP and thiamine respectively.

Folia Microbiol (Praha), 1977, 22(1), 74 - 8
Dependence of yeast sporulation on mitochondrial protein synthesis; Jayachandran S et al.; Sporulation in diploid Saccharomyces cerevisiae is not dependent on continued protein synthesis in the mitochondria . Using chloramphenicol, it is shown that proteins essential for respiration and sporulation are synthesized in mitochondria early during growth in a presporulation medium.

Genetics, 1977 Jan, 85(1), 1 - 22
Role of DNA sequences in genetic recombination in the iso-1-cytochrome c gene of yeast . II . Comparison of mutants altered at the same and nearby base pairs; Moore CW et al.; X-ray-induced mitotic recombination rates and spontaneous meiotic recombination rates have been determined in two-point crosses of various defined cyc1 mutants of the yeast Saccharomyces cerevisiae . All but one of the 17 cyc1 mutants chosen for this study contained either the addition, deletion or substitution of single base-pairs located within a defined segment of the gene that corresponds to the 11 amino acid residues at the amino terminus of iso-1-cytochrome c; approximately half of these mutants had alterations of the AUG initiation codon, some at the same base pair . Up to 66-fold differences in X-ray-induced recombination rates were observed when the same cyc1 mutant was crossed to cyc1 mutants having different alterations in the AUG initiation codon; over a ten-fold difference was observed in series of homologous crosses involving mutants with different changes at the same base-pair . Recombination rates that were associated with specific cyc1 mutants co-segregated with the particular alleles following meiosis, and comparable recombination patterns were also observed for independently isolated, identical mutations . With the mutants used in this study, the frequencies of meiotic recombination did not differ as markedly, suggesting a dissimilar dependence on specific DNA sequences for these two modes of recombination . These disproportionalities of recombination rates suggest that the nature of the mismatched bases influences the recombination process, but not in a way that can be simply interpreted.

Eur J Biochem, 1977 Jan, 72(2), 361 - 9
Terminal nucleotide sequences of 17-S ribosomal RNA and its immediate precursor 18-S RNA in yeast; De Jonge P et al.; The 5' and 3'-terminal nucleotide sequences of 17-S rRNA and its immediate precursor 18-S RNA from the yeast Saccharomyces carlsbergensis have been analysed . Identification of the terminal oligonucleotides, as present in Ti ribonuclease digests, was performed by diagonal procedures . The major (molar yield 0.9) 5'-terminal oligonucleotide (molar yield 0.15) with the overall composition pU (U2,C2)G was observed . 18-S precursor RNA was found to contain the same 5'-terminal sequences as 17-S rRNA . However, the 3'-terminal sequences of the two types of RNA appeared to be different . The 17-S rRNA yields the oligonucleotide A-U-C-A-U-U-AOH while at least half of the 18-S RNA molecules contain the sequence U-U-U-C-A-A-U-AOH . In addition 18-S RNA yields several minor 3'-terminal oligonucleotides which appear to be structurally related to the major 3'-terminal sequence . These results demonstrate that the extra nucleotides in 18-S RNA relative to 17-S RNA are located exclusively at the 3'-terminus of the 18-S RNA molecule . The possibility that the 3'-terminal nucleotide sequence of 18-S RNA plays a role in the maturation process is discussed.

Proc Natl Acad Sci U S A, 1977 Jan, 74(1), 96 - 100
Enzymatic synthesis of oligonucleotides of defined sequence: synthesis of a segment of yeast iso-1-cytochrome c gene; Gillam S et al.; The deoxyribooligonucleotide, d(pT-T-A-G-C-A-G-A-A-C-C-G-G), constituting a segment of yeast iso-1-cytochrome c gene, has been synthesized by a combination of chemical and primarily enzymatic methods . The starting primer, d(pT-T-A-G1, was chemically synthesized by the phosphodiester method and was extended stepwise, by reactions catalyzed by polynucleotide phosphorylase.

Acta Biol Med Ger, 1977, 36(7-8), 1027 - 33
Binding of MgATP to yeast phosphofructokinase; Nissler K et al.; Binding of MgATP to yeast phosphofructokinase was investigated by the gel filtration equilibrium dialysis technique . Per subunit of yeast phosphofructokinase two molecules of MgATP are bound in the absence of fructose-6-phosphate, one to a high-affinity and one to a low-affinity site . The experimental data were compared with a kinetic model of yeast phosphofructokinase as described by Freyer et al . {3}.

Biochimie, 1977, 59(11-12), 869 - 75
Several classes of binding sites for metals and nucleotides on yeast mitochondrial oligomycin sensitive ATPase; Jallon JM et al.; The binding properties of Mg2+, Mn2+ and Co2+ to yeast mitochondrial oligomycin sensitive ATPase complex are studied, as reflected by their catalytic effect (hydrolysis of ATP or pNPP, a pseudo substrate) or by a physical parameter (atomic absorption, electron paramagnetic reasonance of Mn2+, enhanced fluorescence of chelating chlorotetracyclin) . At least two classes of sites with very different affinities respectively around 10(-5) M and 10(-4) M are demonstrated: high affinity sites for cations which participate in pNPP hydrolysis and can bind ADP or ATP, although they have a poor efficiency for ATP hydrolysis, and low affinity sites for cations which participate efficiently in both pNPP and ATP hydrolysis . The possibility that the tight site class has itself two sub-classes is also discussed.

Adv Exp Med Biol, 1977, 95, 271 - 89
Characteristics and functions of proteinase A and its inhibitors in yeast; Holzer H et al.; A purification and some properties of proteinase A from yeast are described . A specific macromolecular inhibitor of proteinase A from yeast cytosol has been isolated and shown to be a protein (molecular weight 7,700) consisting of a majority of polar amino acids . Proline, arginine, cysteine and tryptophan were not detected in the inhibitor . Possible biological functions of proteinase A and the proteinase A-inhibitor (and of other yeast proteinases and their inhibitors) in the following processes are discussed: general protein turnover, catabolite inactivation of enzymes, enzyme degradation at starvation and at transition to spore formation, and activation of pre-enzymes and precursor proteins by limited proteolysis.

Biochem J, 1977 Jan 1, 161(1), 73 - 82
A study of the ionic properties of the essential histidine residue of yeast alcohol dehydrogenase in complexes of the enzyme with its coenzymes and substrates; Dickenson CJ et al.; 1 . Initial-rate studies of the reduction of acetaldehyde by NADH, catalysed by yeast alcohol dehydrogenase, were performed at pH 4.9 and 9.9, in various buffers, at 25 degrees C . The results are discussed in terms of the mechanism previously proposed for the pH range 5.9-8.9 {Dickenson & Dickinson (1975) Biochem . J . 147, 303-311} . 2 . Acetaldehyde forms a u.v.-absorbing complex with glycine . This was shown not to affect the results of kinetic experiments under the conditions used in this and earlier work . 3 . The variation with pH of the dissociation constant for the enzyme-NADH complex, calculated from the initial-rate data, indicates that the enzyme possesses a group with pK7.1 in the free enzyme and pK8.7 in the complex . 4 . The pH-dependences of the second-order rate constants for inactivation of the enzyme by diethyl pyrocarbonate were determined for the free enzymes (pK7.1), the enzyme-NAD+ complex (pK approx . 7.1) and the enzyme-NADH complex (pK approx . 8.4) . The essential histidine residue may therefore be the group involved in formation and dissociation of the enzyme-NADH complex . 5 . Estimates of the rate constant for reaction of acetaldehyde with the enzyme-NADH complex indicate that acetaldehyde may combine only when the essential histidine residue is protonated . The dissociation constants for butan-1-ol and propan-2-ol, calculated on the basis of earlier kinetic data, are, however, independent of pH . 6 . The results obtained are discussed in relation to the role of the essential histidine residue in the mechanism of formation of binary and ternary complexes of the enzyme with its coenzymes and substrates.

J Biochem (Tokyo), 1977 Jan, 81(1), 197 - 205
Studies on the microsomal electron-transport system of anaerobically grown yeast . V . Purification and characterization of NADPH-cytochrome c reductase; Kubota S et al.; A flavoprotein catalyzing the reduction of cytochrome c by NADPH was solubilized and purified from microsomes of yeast grown anaerobically . The cytochrome c reductase had an apparent molecular weight of 70,000 daltons and contained one mole each of FAD and FMN per mole of enzyme . The reductase could reduce some redox dyes as well as cytochrome c, but could not catalyze the reduction of cytochrome b5 . The reductase preparation also catalyzed the oxidation of NADPH with molecular oxygen in the presence of a catalytic amount of 2-methyl-1,4-naphthoquinone (menadione) . The Michaelis constants of the reductase for NADPH and cytochrome c were determined to be 32.4 and 3.4 micron M, respectively, and the optimal pH for cytochrome c reduction was 7.8 to 8.0 . It was concluded that yeast NADPH-cytochrome c reductase is in many respects similar to the liver microsomal reductase which acts as an NADPH-cytochrome P-450 reductase {EC 1.6.2.4}.

J Biochem (Tokyo), 1977 Jan, 81(1), 187 - 95
Studies on the microsomal electron-transport system of anaerobically grown yeast . IV . Purification and characterization of NADH-cytochrome b5 reductase; Kubota S et al.; The presence of NADH-cytochrome b5 reductase {EC 1.6.2.2} in microsomes from anaerobically grown yeast was confirmed by its isolation and purification . The purified preparation of the reductase showed an apparent molecular weight of 27,000 daltons . The reductase appeared to contain loosely-bound FAD as a prosthetic group . The reductase required NADH as a specific electron donor, and could reduce some redox dyes as well as cytochrom b5 . The reductase, however, could not reduce cytochrome c . Michaelis constants of the reductase for NADH and calf liver cytochrome b5 were 6.3 and 1.5 micron M, respectively, and optimal pH for cytochrome b5 reduction was 5.6 . Although some differences exist between the properties of NADH-cytochrome b5 reductase from yeast and from mammalia, the results indicate a functional similarity of the present enzyme to mammalian NADH-cytochrome b5 reductase in the microsomal electron-transport system.

Scand J Dent Res, 1977 Jan-Feb, 85(2), 130 - 4
Denture stomatitis-yeast occurrence and the pH of saliva and denture plaque; Olsen I et al.; The study comprised 30 denture wearers with generalized simple or granular inflammation in the palate and 30 without (controls) . )easts, mostly Candida species, were cultivated from the maxillary dentures of all subjects with inflammation and of 23 controls . Hyphae were found in the maxillary denture smears from 28 subjects with inflammation and from 18 controls . Thus it seems unjustified to consider the occurrence of hyphae pathognomonic of denture stomatitis . The pH of whole saliva did not differ in the two groups (inflammation:mean pH 6.5, control:6.6) . There was no clear relation between the pH of resting saliva and the amount of fungal cultures . Thirty minutes after a mouthrinse with 10 ml of a 25% sucrose solution, the mean saliva pH had dropped equally in both groups . With regard to the denture plaque, samples taken 40 min after the rinse indicated a more pronounced acid production in the plaque associated with inflammation . The pH of "resting" plaque was also lower in the inflammation than in the control group (mean maxillary pH 5.7 and 6.3 respectively, a=0.002) . No association was found between the pH and the occurrence of hyphae in "resting" denture plaque . This supports the view that the pH is of no major importance for filamentation in vivo.

Biochim Biophys Acta, 1976 Dec 22, 453(2), 453 - 8
End group analysis of yeast fatty acid synthetase; Schwietz H et al.; The purified yeast fatty acid synthetase complex has been subjected to amino and carboxyl terminal amino acid end group analysis . Amino end groups were studied by Edman degradation and by dansylation of the sodium dodecyl sulfate- or urea-denatured complex . No N-terminal amino acid could be identified by either method . C-terminal amino acids were investigated by tritium labeling and by digestion of the complex with carboxypeptidases A and B . By both methods, the two amino acids valine and lysine were consistently identified as the C-termini of two different polypeptide chains . After separation of the fatty acid synthetase subunits A and B by sodium dodecyl sulfate polyacrylamide gel electrophoresis lysine was identified as the C-terminus of subunit A and valine as that of subunit B . The results are interpreted as evidence that the yeast fatty acid synthetase complex is basically composed of two nonidentical and multifunctional polypeptide chains.

Eur J Biochem, 1976 Dec 11, 71(2), 425 - 36
Stopped-flow studies of changes in fluorescence of 8-anilino-1-naphthalene sulfonic acid caused by magnesium and salt binding to yeast enolase; Brewer JM; Stopped-flow studies of magnesium and salt (potassium chloride and acetate) effects on yeast enolase were carried out by following 8-anilino-1-naphthalenesulfonic acid fluorescence changes . The fluorescence changes appear to be largely caused by subunit association and dissociation, though there is evidence in some reactions for large changes in fluorescence occurring within the dead time of the stopped-flow measurements . These data are combined with measurements of initial enzyme activity after incubation in various solvents with or without magnesium to obtain subunit association and dissociation rates . From these, it is concluded that magnesium and the salts act by directly changing the affinities of the subunits for each other, apparently by producing a rapid change in protein conformation.

J Biol Chem, 1976 Dec 10, 251(23), 7521 - 5
pH-dependent effects of Cr(NH3)2ATP on kinetics of yeast hexokinase PII . Relationship to the slow transition mechanism; Peters BA et al.; The effect of Cr(NH3)2ATP, a virtually inert, inner sphere metal-ligand complex, on the kinetics of purified yeast hexokinase PII has been studied at pH 6.5 and pH 7.5 . At pH 6.5, where the normal assays exhibit a slow burst-type transient, low concentrations of Cr(NH3)2ATP were found to activate both phii, the initial velocity, and phiII, the steady state velocity . At higher concentrations, Cr(NH3)2ATP was found to be a competitive inhibitor versus MgATP for both phii and phiII . The apparent Ki values for both velocities were the same . The inhibition by Cr(NH3)2ATP at pH 6.5 was found to be a slow process with half-times similar to those found for the normal burst-type transient at this pH value . At pH 7.5, where normal assays exhibit linear progress curves, Cr(NH3)2ATP behaved similarly to that observed before at pH 7 (Danenberg, D . D., and Cleland, W . W . (1975) Biochemistry 14, 28-39), i.e . it was a competitive inhibitor versus MgATP and it caused a slowing of the reaction rate over the first several minutes . The apparent Ki for the initial velocity was 8-fold higher than the apparent Ki for the steady state velocity, suggesting tighter binding of Cr(NH3)2ATP with time . Preincubation experiments indicated that the normal pH 6.5 burst-type transient could be eliminated by appropriate preincubation with Cr(NH3)2ATP and a sugar . In agreement with Danenberg and Cleland (1975), similar preincubations have been shown to produce linear assays at pH 7.5 in the presence of Cr(NH3)2ATP . Similar results were seen with MgITP as the nucleotide substrate, where a burst-type transient is not seen at either pH value under normal assay conditions . At pH 7.5, a slow decrease in the reaction rate is seen over the first several minutes in the presence of Cr(NH3)2ATP . The apparent Ki for phii was 7-fold higher than the apparent Ki value for phiII, again suggesting a tighter binding of Cr(NH3)2ATP with time . A similar observation was made at pH 6.5, but the Ki values for phii and phiII were the same, suggesting no tightening of the binding of Cr(NH3)2ATP with time at this pH value . These results suggested that both slow processes reflect the same basic molecular change, but the consequences are different at the two pH values, presumably because of the difference in the charge of the enzyme . The Cr(NH3)2ATP kinetics at pH 6.5 have been interpreted in terms of a modification of the slow transition mechanism for hexokinase (Shill, J . P., and Neet, K . E . (1975) J . Biol . Chem . 250, 2259-2268) . It is postulated that glucose and Cr(NH3)2ATP induce the same slow conformational change at pH 6.5 as that induced by glucose and MgATP, which gives rise to the normal burst-type transient . This suggests that Cr(NH3)2ATP may be a useful tool for physical studies to determine the cause of the slow transition of yeast hexokinase . Activation by low concentrations of Cr(NH3)2ATP was interpreted as binding of the nucleotide to an activator site on the enzyme, causing a shift in the distribution of enzyme towards the more active form.

Biochim Biophys Acta, 1976 Dec 8, 452(2), 452 - 7
External yeast beta-fructosidase . Affinity labeling of the active site; Braun H; Conduritol-B-epoxide, a compound structurally related to the substrates of external yeast beta-fructosidase (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26), is an active-site directed inhibitor of this enzyme . The inactivation is irreversible and first-order with respect to time and inhibitor concentration . From the kinetic data obtained, it is concluded that one molecule of inhibitor reacts with one molecule of the enzyme causing inactivation . The inactivation is prevented by the presence of substrates . The pH-dependence of inactivation shows two dissociating groups in the enzyme with pKa values 3.05 and 6.8 being involved in the inactivation process . A carboxylate at the active site with pKa 3.05 is suggested to be the reactive group with conduritol-B-epoxide.

Arch Microbiol, 1976 Dec 1, 111(1-2), 193 - 4
A note on the kinetics of uptake of D-glucose by the food yeast, Candida utilis; Barnett JA et al.; Unlike other yeasts so far investigated, the D-glucose carrier of Candida utilis (strain NCYC 737) appears to change affinity for D-glucose according to its exogenous concentration . When the concentration of D-glucose was less than 0.4 mM, the apparent Km approximately 0.2 mM; at greater than 0.4 mM, the Km approximately 10 mM.

J Bacteriol, 1976 Dec, 128(3), 851 - 2
Detection, with the dye phloxine B, of yeast mutants unable to utilize nitrogenous substances as the sole nitrogen source; Middelhoven WJ et al.; Yeast mutants unable to degrade certain nitrogen compounds produce characteristic small red colonies on an agar medium containing the red dye phloxine B, galactose, the test nitrogen compound, and a small amount of ammonium chloride.

Proc Natl Acad Sci U S A, 1976 Dec, 73(12), 4334 - 8
Interaction of integral and peripheral membrane proteins: affinity labeling of yeast cytochrome oxidase by modified yeast cytochrome c; Birchmeier W et al.; To identify possible substrate-binding subunit(s) of yeast cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1-9-3-1), the purified enzyme was reacted with yeast iso-1-cytochrome c whose single free sulfhydryl group at position 107 had been activated with 5,5'-dithiobis(2-nitrobenzoate) . The resulting cytochrome c derivative appeared to function as an "affinity-label" of cytochrome oxidase, since it rapidly inactivated the enzyme . Inactivation was competitively prevented by underivatized cytochrome c . When the "affinity-labeled" oxidase was analyzed by two-dimensional polyacrylamide electrophoresis in dodecyl sulfate (separation in the second dimension being carried out in the presence of excess sulfhydryl compound), it was found that the derivatized cytochrome c had specifically formed a mixed disulfide with the mitochondrially made subunit III (apparent molecular weight 24,000) of the oxidase . Similar results were obtained when underivatized iso-I-cytochrome c was crosslinked to the oxidase by oxidative disulfide bridge formation in the presence of ortho-phenanthroline and Cu++ . These data indicate that the hydrophobic mitochondrially made subunit III of yeast cytochrome c oxidase is in close proximity to the cytochrome c binding site on the enzyme . Since cytochrome c and the mitochondrially made cytochrome oxidase subunit III are typical peripheral and integral membrane proteins, respectively, the present study suggests a useful approach for analyzing specific interactions between these different classes of membrane proteins.

Biokhimiia, 1976 Dec, 41(12), 2173 - 8
{Cytosolic alcohol dehydrogenases from yeast Torulopsis candida}; Sudovtsov VE; A comparative study of cell cytosol alcohol dehydrogenase (ADH) from yeast Torulopsis candida IBFM-Y-127 grown on glucose and hexadecane which were the only source of carbon, was made . In both cases ADH had a pH optimum within the range of 7.0--10.0, when various normal primary alcohols (C2--C16) were used . The enzyme was active only in the presence of NAD, which cannot be substituted by NADP . The total activity of ADH decreased approximately 8-fold when the length of hydrocarbon radicals was changed from C2 up to C16 . When the cells were grown on hexadecane, only ethyl, n-buthyl, n-amyl and n-hexyl alcohols were active as substrates . The dehydration rate of each alcohol was far lower than that for the cytosol of glucose-grown cells . In the latter case the enzyme activity also decreased with an increase in the alcohol radical from C2 to C6 . In all cases studied methyl alcohol and cyclic (cinnamyl alcohol--C8) alcohol were not dehydrated at all . Disc-electrophoresis in polyacrylamide gel, involving gel colouration for the assay of enzyme activity showed that glucose--grown cell cytosol contained three forms of ADH . One of those forms was highly active when short--chain normal primary alcohols were used; this form may be probably regarded as "classical" ADH (EC 1.1.1.1) . The two other forms caused intensive dehydration of long-chain alcohols (the best substrates were C7--C10 alcohols for one form and C10--C14 for the others) . The two forms of ADH are probably isoenzymes of octanol dehydrogenase (EC 1.1.1.73) . Cytosol of cells grown on n-alcane, had a reduced number of ADH forms . The data obtained are discussed in terms of the regulatory role of carbon and energy source (glucose or hexadecane) in the redistribution of alcohol dehydrogenases between structural components of cells (mitochondria) and cytosol.

Hoppe Seylers Z Physiol Chem, 1976 Dec, 357(12), 1771 - 7
Effects of yeast proteinase A, proteinase B and carboxypeptidase Y on yeast phosphofructokinase; Afting EG et al.; Incubation of a crude yeast extract containing phosphofructokinase with proteinase A, proteinase B or carboxypeptidase Y gave the following results: Proteinase B and carboxypeptidase Y did not change the activity of phosphofructokinase during incubation . On the other hand, incubation with proteinase A resulted in a 40-100% activation; continued incubation, however, led to an inactivation of the enzyme . Addition of allosteric effectors did not change the activation or inactivation process . The activated phosphofructokinase was not changed with respect to pH optimum and ATP inhibition . Molecular weight determination of phosphofructokinase in crude extracts in the presence of inhibitors of proteinase A indicated a molecular weight of 700000 . Without inhibitors of proteinase A, the molecular weight was determined to be 600 000, while after 40-100% activation by proteinase A, a molecular weight of 500 000 was obtained . The activity profile of proteinase A in density gradients indicated that this enzyme is bound to variety of cellular proteins.

Mol Cell Biochem, 1976 Nov 30, 13(2), 73 - 8
Determination of intermediary metabolites in yeast . Critical examination of the effect of sampling conditions and recommendations for obtaining true levels; Saez MJ et al.; The effect of sampling conditions on the levels of adenine nucleotides, pyridine nucleotides, glycolytic intermediates and related metabolites in yeast has been studied . A systematic examination of the conditions for harvesting has shown that it can be best accomplished by rapid filtration . Delays in the handling for removal of the medium, as is usual in the process of obtaining a number of data reported in the literature, lead to important changes in some of the metabolites examined . It is also shown that when a washing is imperative it can be carried out with a methanol-water mixture (50/50, v/v) cooled at -40 degrees without loss of intracellular concentrations of non-readily diffusible metabolites . On the basis of this experience the outline of a generally applicable procedure is presented.

J Biol Chem, 1976 Nov 25, 251(22), 7157 - 61
Interaction of tetraiodofluorescein with yeast hexokinase; Yip BP et al.; The dye tetraiodofluorescein (TIF) was found to be an effective inhibitor of yeast hexokinase . It is a competitive inhibitor relative to MgATP2- and a noncompetitive inhibitor of glucose binding, a kinetic pattern consistent with the previously proposed random kinetic mechanism . TIF interacts directly with the native dimeric protein to give a difference spectrum with a maximum at 543 nm . Monomeric protein (produced by addition of 0.6 M NaCl) interacts with TIF to give a slightly altered difference spectrum, with the gammamax at 545 nm . The difference spectrum of the dimeric form is not perturbed by the addition of substrates but the absorbance with the monomer is lowered by MgATP2- . The Kd for MgATP2- was estimated to be 7 nM for monomeric hexokinase . These results suggest that results of previous binding studies with hexokinase at high concentrations which have been interpreted as being at variance with kinetic studies are due likely to different conformations of the protein under different experimental conditions.

Eur J Biochem, 1976 Nov 15, 70(2), 385 - 95
Protein degradation during yeast sporulation . Enzyme and cytochrome patterns; Betz H et al.; The levels of several enzymes have been studied during sporulation of Saccharomyces cerevisia . The specific activities of ribonuclease and aminopeptidase I raised several-fold after transfer of the cells to sporulation medium, whereas the specific activities of phosphofructokinase, glucose-6-phosphate dehydrogenase, tryptophan synthase and pyruvate decarboxylase were not significantly altered . The specific activities of NAD-dependent glutamate dehydrogenase, isocitrate lyase, malate dehydrogenase and fructose bisphosphatase all decreased from the onset of sporulation . The inactivation of these latter enzymes was inhibited by cycloheximide and by inhibitors of energy metabolism . Hexokinase, alcohol dehydrogenase and glutamate oxaloacetate transaminase were partially lost from the cells during the period of ascus maturation . None of the enzyme changes observed proved to be 'sporulation-specific' in that it occurred exclusively in sporulating diploid yeast cells . Therefore it is postulated that the meiotic events and the metabolic changes required for ascospore formation are under separate genetic control in this organism . During sporulation, the cellular content of cytochromes b, c, and aa3 was reduced to 20% or less of that present in vegetative derepressed cells . Since the relative percentage of total to cycloheximide-insensitive mitochondrial protein synthesis was not significantly altered throughout sporulation, and the pattern of mitochondrially synthesized polypeptides was rather similar both in vegetative and in sporulating cells, it appeared that not only degradation but also synthesis and therefore turnover of the mitochondrially coded polypeptides of cytochromes b and aa3 took place during sporulation . The activity ratio of cytochrome c oxidase to F1-ATPase in submitochondrial particles isolated from vegetative cells and from purified asci was almost identical . This indicates that the loss of membrane-bound mitochondrial cytochromes during sporulation is probably due to a nonselective degradation of inner mitochondrial membrane proteins.

Arch Microbiol, 1976 Nov 2, 110(23), 313 - 8
Mating reaction in yeast protoplasts; Svoboda A; Protoplasts prepared from complementary haploid strains of Saccharomyces cervisiae were studied with regard to their ability of conjugating . Neither fresh protoplasts nor the growing protoplasts possessing fibrillar walls exhibited sex specific agglutination or fusion . However, they were capable of inducing sexual activation in normal cells of opposite mating type . After completing the regeneration of cell walls the protoplasts could conjugate either with each other or with cells of opposite sex . The frequency of conjugations was low, about 1%, and was largely dependent on the degree of completition of the wall during regeneration . From the results the following conclusions may be drawn: 1 . The initiation of mating is dependent on the integrity of the cell wall . 2 . The sex specific morphogenetic changes do not occur in wall-less protoplasts but may happen after the protoplasts have regenerated their cell walls . 3 . The lysis of cell walls does not occur until the walls come into close contact . 4 . The fusion of plasma membranes in sex-activated protoplasts cannot be induced by arteficial agglutination.

Biochemistry, 1976 Nov 2, 15(22), 4760 - 4
A cycloheximide sensitivity factor from yeast required for N-acetylphenylalanylpuromycin formation; Somasundaran U et al.; A protein (factor P) has been isolated from yeast, which was required for sensitivity to cycloheximide of a partially purified polyphenylalanine synthesis system . In the absence of factor P, 10(-3) M cycloheximide was required for 50% inhibition of polyphenylalanine synthesis, while in its presence, 10(-6) M gave 50% inhibition . Coincident with cycloheximide sensitivity was an activity required for EF-2 dependent N-acetylphenylalanylpuromycin (N-AcPhePuro) formation . Transfer of N-AcPhe to puromycin from the tRNA bound in the presence of 26 mM MgCl2 required factor P, as well as EF-2 . Studies with antibody against EF-2 demonstrated that P factor was not required during the EF-2 translocation step but for some subsequent step.

Biochemistry, 1976 Nov 2, 15(22), 4881 - 5
Reaction of yeast carboxypeptidase C1 with group-specific reagents; Kuhn RW et al.; The reactions between yeast carboxypeptidase C and the group-specific reagents, phenylglyoxal and iodoacetamide, have been studied in detail and the reactions of residue at the active site with N-tosyl-L-phenylalanine chloromethyl ketone and diisopropyl phosphorofluoridate have been confirmed . Modification of the enzyme by either phenylglyoxal or iodoacetamide results in the loss of peptidase activity, while esterase activity remains unchanged . Inactivation by phenylglyoxal appears to be the result of the modification of a single arginine residue, whereas inhibition by iodoacetamide can be correlated with the modification of a single methionine residue . Inactivation of the enzyme by either N-tosyl-L-phenylalanine chloromethyl ketone or diisopropyl phosphorofluoridate is the result of the modification of a single histidine and a single serine residue, respectively . The pattern of inhibition indicates certain analogies in the mechanism of yeast carboxypeptidase C to pancreatic chymotrypsin, on the one hand, and to carboxypeptidase A, on the other.

Mikrobiologiia, 1976 Nov-Dec, 45(6), 1040 - 4
{Biological productivity of hybrids and strains of yeast cultures of different ploidy}; Kosikov KV et al.; Ploidy and productivity of yeast strains and hybrids obtained by crossing various industrial races were studied . Biological productivity of yeast cultures increases with ploidy as was found by comparing biological productivity (biomass accumulation) in haploids, diploids, triploids, and tetraploids . Possible factors causing an insignificant decrease in productivity of some tetraploids as compared to triploids are discussed.

Mikrobiologiia, 1976 Nov-Dec, 45(6), 1018 - 22
{Studies of the primary distribution kinetics of n-alkane oxidation products according to morphological components of the yeast cell}; Davidova EG et al.; Incorporation of 14C into various classes of lipids localized in the cell walls, large membranes, mitochondria and microsomes of yeast cells was studied during their incubation with 1-14C-octadecane . Cell structures were found to differ considerably by the kinetics and level of accumulation of 14C-components of the lipid fraction . Waxes and triglycerides prevail during primary accumulation of 14C-lipids in the large membranes and cell walls . Synthesis of these compounds is presumed to play an important role in the course of primary transformation of n-octadecane.

Br J Nutr, 1976 Nov, 36(3), 471 - 8
The digestion of yeast cell wall polysaccharides in veal calves; Gaillard BD et al.; 1 . The digestibility of the cell wall polysaccharides of an alkane-grown yeast in different parts of the digestive tract of two veal calves fitted with re-entrant cannulas at the end of the ileum was studied by replacing part of the skim-milk powder of their 'normal', milk-substitute (all-milk-protein) diet by yeast (yeast diet) . 2 . The lactose and glucose of both the all-milk-protein diet and the yeast diet were almost completely digested before the end of the ileum . During this digestion a small amount of oligosaccharides composed of galactose and glucose was synthesized . These oligosaccharides were digested again in the large intestine . 3 . The constituent sugars of the water-soluble fraction of the yeast cell wall carbohydrates were glucose and mannose . The 0-5 M-sulphuric acid-hydrolysate of the water-insoluble fraction contained glucose and mannose and the 12 M-H2SO4-hydrolysate only glucose . 4 . Digestibilities measured at the end of the ileum varied considerably between the two animals and averaged only about 0-40 . 5 . These findings suggest that the cell wall polysaccharides of yeast are digested very little by the normal digestive enzymes of the calf's small intestine, but are used as a substrate by the bacterial flora which are mainly concentrated in the large intestine.

Clin Chem, 1976 Nov, 22(11), 1802 - 5
Spectrophotometric and electrochemical determinations of L(+)-lactate in blood by use of lactate dehydrogenase from yeast; Durliat H et al.; Lactate can be determined rapidly in blood by spectrophotometric and amperometric (enzyme electrode) procedures based on its oxidation by ferricyanide, the reaction being catalyzed with yeast L(+)-lactate dehydrogenase (cytochrome b2) (EC 1.1.2.3) . In the photometric method lactate can be measured in a few minutes, but blood samples must first be deproteinized . In the amperometric procedure no treatment of blood is needed except ferricyanide addition . The enzyme electrode we used has a response time shorter than 1 min when its critical variables are optimized . Preliminary standardization is reduced to minimum operation, because electrode response is proportional to lactate concentration over a wide range (0.1 to 8.0 mol/liter) and many determinations can be done with little cost in enzyme . A simple electrical device ("two-electrode device") is described that is well suited for furture micro-cell construction . Lactate determinations on a series of normal blood samples show no deviation between results by these new methods and the usual ultraviolet spectrophotometric lactate tests.

Mol Biol (Mosk), 1976 Nov-Dec, 10(6), 1260 - 71
{Complementarily addressed alkylation of yeast tRNA 1 Val with chloroethylmethylaminobenzylidene d(pC-G)-A . Proof of the modification of the third nucleotide located at the 5'-terminus of the complete binding site of the reagent}; Grineva NI et al.; Yeast tRNAlVal alkylation with 2',3'-0-{4-(N-2-chloroethyl-N-methylaminobenzylidene}dpCdpGrpA proceeds within complementary complexes that are formed due to attachment of the reagent to three sequences of tRNAlVal . The acetal bond of the initial product of alkylation has been hydrolyzed to yield beta-{N=methyl-N-(4-formylphenyl) amino}ethyl-tRNAlVal (R-tRNA) that contains from 1 to 3 residues of the specifically modified nucleosides: alkyl adenosine (R-A), R-I and probably R-psi . Individual alkylated oligonucleotides were isolated from R-tRNAlVal pyrimidyl-RNAse digest . The alkylated oligonucleotides correspond to 93% of all modified products . The major component is beta-{N-methyl-N(4-formylphenyl)aminoA1ethyl-A53-G-Tp . This indicates that the reagent is attached to complementary psi-C-G-sequence in the T-loop of tRNAlVal and that alkylation of the third nucleotide counting from the 5'-terminus of the sequence which binds the reagent completely takes place within the complementary complexes . This site of the tRNAlVal is modified quantitatively at 20 degrees and 19-fold excess of the reagent . The alkylation of two other sites of tRNA reaches 50% under these conditions.

Eur J Biochem, 1976 Nov 1, 70(1), 25 - 31
Calorimetric investigations on thermal stability of tRNAIle (yeast) and tRNASer (yeast); Filimonov VV et al.; Variation with temperature of the partial heat capacities of tRNAIle (yeast) and tRNASer (yeast) has been determined in two buffers at various salt conditions by scanning microcalorimetry . The overall molar transition enthalpy, deltaHt = 320 +/- 20 kcal mol-1 (1339 +/- 84 kJ mol-1) is identical for the two tRNA species within the limits of experimental error . deltaHt does not show any dependence on the nature of the buffer, nor does it vary on addition of 1 mM MgCl2 or 150 mM NaCl . Thermal unfolding of the native structure to the random coil cannot adequately be described by a two-state, concerted transition under the experimental conditions applied in this study, but exhibits a multistep mechanism characterized by sequential unfolding of separable cooperative domains.

Mutat Res, 1976 Nov, 37(2-3), 193 - 200
Effect of dimethyl sulfoxide (DMSO) on radiation-induced heteroallelic reversion in diploid yeast; Singh DR et al.; Dimethyl sulfoxide has cryoprotective and radioprotective properties . It is also an efficient scavenger of radicals produced by raiolysis of water . Gamma-induced reversions of diploid yeast in the presence of this chemical during irradiation have been studied . The dose-modifying factor was in the same range as for survival . When the yeast was irradiated in the frozen state the observed protection by DMSO disappeared . The results are discussed in terms of direct and indirect actions of radiations and the radical-scavenging ability of this chemical.

Proc Natl Acad Sci U S A, 1976 Nov, 73(11), 3933 - 6
Acitivity of yeast extracts in cell-free stimulation of DNA replication; Jazwinski SM et al.; Extracts of the cytoplasm of disrupted spheroplasts of Saccharomyces cerevisiae (bakers' yeast) stimulated DNA synthesis in a cell-free system consisting of nuclei from spleen cells of the frog Xenopus laevis, The stimulation required Mg++8 ATP, and the deoxynucleoside triphosphates, was saturated by an excess of nuclei or extract, and had kinetics resembling those obtained previously with extracts from mammalian and avian cells . After addition of the yeast extract, replication "eyes" were formed in the DNA from the nucleochromatin of the frog, suggesting that the extract stimulated the initiation of DNA replication . The activity was susceptible to heat, was nondialyzable, and was abrogated by tryptic digestion . Temperature-sensitive mutants of the cell division cycle (cdcmutants 4,7,8, and 28) grown at permissive temperature (23 degrees) yielded extracts that were capable of stimulating DNA replication . When the cells were incubated for one generation at the nonpermissive temperature (36 degrees), their extracts showed very low or no activity . All of these mutants are deficient in events of the dependent pathway leading to initiation of DNA synthesis in the yeast cell cycle . A ts mutant, cdc10, deficient in the separate pathway for cytokinesis, showed little or no loss of activity at the nonpermissive temperature . These data indicate that the "initiation" activity, as assayed in vitro, is subject to control in the yeast cell cycle, and its appearance may be one of the terminal events in the pathway leading to DNA synthesis . The finding that extracts from yeast cells can stimulate DNA synthesis in nucleochromatin from frog cells, and the fact that the cdc mutants 4,7,8, and 28 describe a dependent pathway terminating in development of "initiation" activity, are in accord with the hypothesis that the function of proteins in the dependent pathways of the cell cycle is conserved during evolution.

Proc Natl Acad Sci U S A, 1976 Nov, 73(11), 3928 - 32
Negative homotropic cooperativity and affinity heterogeneity: preparation of yeast glyceraldehyde-3-phosphate dehydrogenase with maximal affinity homogeneity; Gennis LS; A three-step procedure including affinity chromatography on NAD+-azobenzamidopropyl-Sepharose has been designed for the purification of yeast glyceraldehyde-3-phosphate dehydrogenase {D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12} with maximized specific activity and maximized homogeneity with respect to affinity for the coenzyme, NAD+.Binding isotherms allow the analysis of cooperativity patterns that disclose both the average ligand affinity in the system and the distribution of ligands among the sites, only for systems with complete affinity homogeneity . The presence of affinity heterogeneity, resulting from multiple oligomeric species differing only in their affinity for coenzyme, gives rise to isotherms which falsely manifest apparent negative cooperativity . A method for distinguishing negative homotropic cooperativity from affinity heterogeneity is suggested.

J Biol Chem, 1976 Oct 25, 251(20), 6320 - 6
Yeast cytochrome c messenger RNA . In vitro translation and specific immunoprecipitation of the CYC1 gene product; Zitomer RS et al.; An assay based upon indirect immunoprecipitation has been developed for yeast cytochrome c and apocytochrome c . The specificity of this assay was demonstrated by its ability to selectively precipitate cytochrome c from an autolysate of yeast cell proteins . Translation of the polypeptide chain of cytochrome c in a wheat germ extract programmed with yeast poly(A) RNA was demonstrated using this immunoprecipitation assay . Translation of poly(A) RNA from yeast strains carrying nonsense mutations in the cyc1 gene yielded in vitro cytochrome c polypeptides which were shorter than the wild type protein by the amount expected for polypeptide chains which had terminated at the nonsense codon . The in vivo rate of cytochrome c synthesis was shown to be 6-fold greater in derepressed cells than in glucose-repressed cells . The 6-fold difference is sufficient to account for the 6-fold higher level of cytochrome c in derepressed than in repressed cells . The level of translatable cytochrome c mRNA is at least 4 times as high in derepressed as in glucose-repressed cells, suggesting that regulation occurs at some step in the synthesis of this messenger.

Science, 1976 Oct 22, 194(4263), 433 - 5
Nuclear and mitochondrial DNA replication during zygote formation and maturation in yeast; Sena E et al.; Nuclear and mitochondrial DNA replication were monitered during the development of synchronous yeast zygotes . Purified first zygotic buds were also analyzed . Nuclear DNA replicated discontinuously but coincidently with bud initiation, while mitochondrial DNA replicated throughout the zygotic formation and maturation period . First zygotic buds contained the diploid level of both nuclear and mitochondrial DNA.

Biochim Biophys Acta, 1976 Oct 18, 447(3), 294 - 303
Ribosomal subunit entry into polysomes in yeast; Petersen N et al.; The kinetics of entry of newly synthesized 40 S and 60 S ribosomal subunits into yeast polysomes is described . The entry times for 40 S and 60 S subunits were found to be 3 and 8 min, respectively . The kinetics of entry of 40 S subunits into large polysomes is found to be different from the kinetics of entry of 60 S subunits into large polysomes.

Biochem J, 1976 Oct 15, 160(1), 37 - 41
Glycosylation in vitro of an asparagine sequon catalysed by preparations of yeast cell membranes; Khalkhali Z et al.; Preparations of yeast cell membranes can catalyse in vitro the N-acetyl-beta-D-glucosaminylation of the asparagine sequon at residues 34--36 of bovine pancreatic ribonuclease A . The relevant glycopeptides were isolated from tryptic hydrolysates of the glycosylated ribonuclease and analysed . The donor used was UDP-N-acetyl-D-glucosamine, although the mechanism of the transfer is unknown . Mn2+ ions at concentrations of 25 mM double the activity of the enzymic transfer.

Radiat Environ Biophys, 1976 Oct 7, 13(3), 167 - 75
Liquid holding recovery in stationary and log phase cultures of diploid yeast exposed to gamma and alpha radiations; Reddy NM et al.; The kinetics of liquid-holding recovery (LHR) in diploid yeast after gamma and alpha irradiation is studied . In case of stationary phase culture the rate and extent of LHR is found to be greater for gamma-ray-induced damage than for alpha-ray-induced damage . At 10% survival level, the half-time for recovery is 5.2 h for gamma-ray damage and 12 h for alpha-ray damage . Further, while the recovery factor for alpha damage reaches saturation at 5% survival level, that for gamma damage continues to increase as survival level decreases . Oxygen is required for the recovery process during LH after gamma irradiation . The cells can recover to the same extent from both oxygen-dependent and oxygen-independent components of damage . Log phase cells containing a high per cent of budding cells, however, exhibit negative liquid holding effect after gamma irradiation.

J Biochem (Tokyo), 1976 Oct, 80(4), 805 - 9
The aconitase of yeast . V . The reconstitution of yeast aconitase; Suzuki T et al.; The apoenzyme of yeast aconitase {EC 4.2.1.3} was prepared by treatment of yeast aconitase with sodium mersalyl, followed by passage by passage of the reaction mixture through a column of Dowex A-1 and gel filtration on Sephadex G-25 . The apoenzyme had no aconitase activity, but the active enzyme could be reconstituted by treatment of the apoenzyme with ferrous ions and sodium sulfide in the presence of 2-mercapto-ethanol . The reconstituted active enzyme was isolated by DEAE-Sephadex A-50 column chromatography and Sephadex G-100 gel filtration from the reaction mixture . The reconstituted enzyme was identical with the original untreated enzyme in terms of specific activity, iron content and spectral characteristics, but not in terms of labile sulfur content . A significant difference in visible spectra between the holo- and apoenzymes appeared to be due to the difference in iron and labile sulfur contents between the two proteins.

J Biochem (Tokyo), 1976 Oct, 80(4), 799 - 804
The aconitase of yeast . IV . Studies on iron and sulfur in yeast aconitase; Suzuki T et al.; Chemical analyses were carried out to determine the active components of the crystalline aconitase {EC 4.2.1.3} of Candida lipolytica . The enzyme contained 2 atoms of non-heme iron, 1 atom of labile sulfur, and 6 sulfhydryl groups per molecule . One atom of the non-heme iron was released by the addition of metal-chelating agents such as sodium citrate, sodium nitrilotriacetate (NTA) or sodium ethylenediaminetetraacetate (EDTA) without loss of the enzyme activity . The non-heme iron and labile sulfur were released by the addition of sulfhydryl reagents such as rho-chloromercuribenzoate (PCMB), sodium mersalyl or urea with loss of the enzyme activity . o-Phenanthroline reacted with the iron atoms in the enzyme at pH 6.0 with loss of the activity . These results show that yeast aconitase is an iron-sulfur protein and that only one of the two non-heme iron atoms is essential for enzyme activity.

Nucleic Acids Res, 1976 Oct, 3(10), 2697 - 707
Topographical analysis of yeast ribosomal DNA by cleavage with restriction endonucleases . II . The physical map of EcoRI fragments; Meyerink JH et al.; Yeast ribosomal DNA (rDNA) was digested with the restriction endonuclease EcoRI . Eight distinct fragments were obtained with a molecular weight of 4.35 (1), 1.75 (2), 1.45 (3), 1.07 (4), 0.42 (5), 0.37 (6), 0.26 (7) and 0.22 x 10(6) (8) daltons, respectively . Except for fragment 1 with a molecular weight of 4.35 x 10(6) daltons, all fragments are derived from the multiple ribosomal transcription units . The 'spacer' sequences, on the other hand, gave rise to digestion products which are very heterogeneous in size . By analysis of the partial digestion products which are very heterogeneous in size . By analysis of the partial digestion products, together with the data obtained by digestion with a combination of two restriction enzymes (EcoRI and Hind II or Hind III) and redigestion of the Hind II-and Hind III-fragments with EcoRI, the physical map of the EcoRI cleavage sites in the ribosomal transcription unit could be established.

Biotechnol Bioeng, 1976 Oct, 18(10), 1337 - 49
Growth kinetics of a yeast grown on glucose or hexadecane; Mason TJ et al.; The kinetics of growth of a Torulopsis sp . was investigated in a continuous culture with glucose or hexadecane as the carbon source; growth was limited by either carbon or nitrogen . The relationship between the concentration of the limited substrate and the steady-state growth rate of the organism was examined and tested against various models of growth . No existing model was found to describe the growth accurately and a new model has been proposed: (see article) . It is postulated that this behavior would result from a simple first order reaction between the reactants of the rate-limiting enzymic reaction of the organism's metabolism.

J Biochem (Tokyo), 1976 Oct, 80(4), 787 - 97
O-Acetylserine and O-acetylhomoserine sulfhydrylase of yeast . Subunit structure; Yamagata S; The molecular weight of O-acetylserine (OAS)-O-acetylhomoserine (OAH) sulfhydrylase purified from yeast was estimated to be about 200,000 by Sephadex G-200 gel chromatography in various buffers . The S20, w value of this protein was determined to be about 9.0 by sucrose density gradient centrifugation . The calculated molecular weight based on this value was similar to that estimated by gel chromatography . Treatment with 1% sodium dodesylsulfate (SDS) or 6 M urea dissociated the enzyme into 4 subunits; these had a molecular weight estimated to be 51,000 by SDS-poly-acrylamide gel electrophoresis and to be 57,000 by Sephadex G-100 gel chromatography in the presence of 6 M urea and 0.5% beta-mercaptoethanol . The 4 subunits appeared to be identical, based on the symmetric subunit elution pattern from a Sephadex column, a single peptide band on SDS-polyacrylamide gel, and the detection of histidine as the sole N-terminal amino acid in the native enzyme . Since dissociation into the subunits occurred without the use of reducing agents, the association of the subunits seems to require no disulfide linkage . One mole of the subunit contained one mole of sulfhydryl group which appeared to be buried inside the molecule . Partial restoration of the catalytic activity was observed when the urea-denatured enzyme was dialyzed to remove urea, especially in the presence of reducing agents such as dithiothreitol . The urea-denatured enzyme showed a tendency in the absence of reducing agents to form a subunit dimer linked by a disulfide bond between the cystine residues exposed by denaturation . The amino acid composition of the enzyme was determined; it contained one half-cystine residue per subunit, and the content of acidic residues was much higher than that of basic residues . Based on these findings, the subunit structure of the enzyme is discussed.

J Biochem (Tokyo), 1976 Oct, 80(4), 777 - 85
O-Acetylserine and O-acetylhomoserine sulfhydrylase of yeast . Further purification and characterization as a pyridoxal enzyme; Yamagata S et al.; O-Acetylserine-O-acetylhomoserine sulfhydrylase {EC class 4.2.99}, catalyzing the sulfhydrylation of both O-acetyl-L-serine (OAS) and O-acetyl-L-homoserine (OAH) (O-acetyl-L-serine(O-acetyl-L-homoserine) + H2S leads to L-cysteine (L-homocysteine) + acetate), was extracted and purified from bakers' yeast by an improved method . The purified enzyme was shown to be homogeneous on polyacrylamide gel electrophoresis both in the absence and presence of sodium dodecylsulfate and by ultracentrifugal analysis . The apo-enzyme was protected by pyridoxal phosphate (PALP) from inactivation by heat, urea, and trypsin {EC 3.4.21.4}, suggesting that the binding of PALP to the apo-enzyme rendered the conformation of the protein more stable . The holo-enzyme showed absorption peaks at 420 and 330 nm due to bound PALP, in addition to a peak at 280 nm . Upon reduction with borohydride, the 420-nm peak disappeared and an increase in the 330-nm peak occurred concomitant with loss of the catalytic activity . Lysine appeared to be the pyridoxal binding site, based on identification of pyridoxyl-lysine in the hydrolyzate of the holo-enzyme . It was shown by both spectral and chemical determinations that 4 moles of PALP could bind to 200,000 g of apo-protein . The apo-enzyme showed a lower association constant with PALP than some other enzymes . Pyridoxal inhibited the activity competitively with respect to PALP . Based on these findings, it appears that the reaction mechanism of this enzyme is similar to those of other pyridoxal enzymes.

Genetics, 1976 Oct, 84(2), 311 - 7
Glucosamine resistance in yeast . I . A preliminary genetic analysis; Ball AJ et al.; Mutants of the yeast Saccaromyces cerevisiae which can grow on glycerol medium in the presence of 0.05% D (+) glucosamine have been isolated . Genetic analysis of 13 of these glucosamine resistant (GR) mutants demonstrated two modes of inheritance . One group of mutants (GR 5, 6, 7, 8, 9 and 10) gave results characteristic of non-Mendelian inheritance and it is suggested that these mutants represent one or more new mitochondial loci . Four of the remaining mutants showed clear-cut Mendelian inheritance . These mutants fell into two complementation groups and subsequent mapping experiments demonstrated that two independent loci, gay 1 and gay 2, unlinked to each other or to the centromeres of chromosomes I, II, IV, VIII or IX, were responsible for conferring glucosamine resistance in these mutants.

Nucleic Acids Res, 1976 Oct, 3(10), 2471 - 84
Mechanisms of chain folding in nucleic acids . The (omega, omega) plot and its correlation to the nucleotide geometry in yeast tRNAPhe1; Sundaralingam M et al.; The (omega', omega) polot depicting the internucleotide P-O bond rotation angles in yeast phenylalanyl transfer RNA has established the interdependence of the phosphodiesters and the nucleotide geometries in the folding of the polynucleotide backbone . The plot distinguishes the regions characteristic of secondary helical structures and tertiary structural loops and bends . The folding of the polynucleotide chain is accomplished either solely by rotations around the P-O bonds or in concert with rotations around the nucleotide C4'-C5' bond with or without changes in the sugar ring pucker . In spite of differences in nucleotide sequence and intraloop tertiary interactions in the anticodon and pseudouridine loops, a characteristic repeating structural unit is found for the sugar-phosphate backbone of the tetranucleotide segment around the sharp turns.

Nucleic Acids Res, 1976 Oct, 3(10), 2427 - 36
The 5' ends of yeast killer factor RNAs are pppGp; Bruenn J et al.; The 5' nucleotides of the double-stranded RNAs of yeast killer factor have been isolated by digestion with pancreatic, T1 and T2 RNase followed by two-dimensional electrophoresis . They were identified by bacterial alkaline phosphatase and snake venom phosphodiesterase digestions . Both the larger double-stranded RNA (L, of 2.5 x 10(6) daltons) and the smaller double-stranded RNA (M, of 1.4 x 10(6) daltons) have the 5' end groups pppGp . These 5' ends are dissimilar to those of the double-stranded RNAs of animal viruses but may be characteristic of the 5' ends of the double-stranded RNAs of fungal viruses.

Appl Environ Microbiol, 1976 Oct, 32(4), 498 - 504
Mercurial toxicity in yeast: evidence for catabolic pathway inhibition; Brunker RL; Evidence that the mechanism of mercurial toxicity is a blockage of catabolic metabolism is presented . Yeast cells (Saccharomyces cerevisiae) were found to cease respiratory activities within 1.5 min of contrast time with culture mercurials (as HgCl2) . This cessation was followed by the rapid depletion of endogenous adenosine 5'-triphosphate (ATP) and a concomitant increase in phosphorylated hexoses . Levels of ATP in the culture medium remained essentially unchanged during this interval suggesting that the structural integrity of the membrane was not affected . Medium potassium concentrations did not increase until after endogenous ATP levels had begun to fall, suggesting that the loss of cellular potassium was the result of the inability of membrane ATPases to function because of the unavailability of sufficient substrate ATP to maintain this gradient.

Biokhimiia, 1976 Oct, 41(10), 1784 - 7
{Phosphorylation of some thiamine analogs by yeast thiamine pyrophosphokinase}; Voskoboev AI et al.; A rapid efficient method of separation of the thiamine pyrophosphokinase reaction products (ATP: thiamine pyrophosphotransferase) on the column packed with DEAE-Sephadex A-25 and their subsequent identification by direct spectrophotometry is suggested . Phosphorylation of some thiamine analogs substituted at the second position of the pyrimidine ring was studied . It was shown that in addition to thiamine, the enzyme transfers the pyrophosphate group to some of its derivatives . The vitamin analogs devoid of quaternary nitrogen in the thiazole cycle, do not form pyrophosphate ethers (thus being unable to act as substrates), whereas 2'-phenoxythiamine, 2'-methoxythiamine and especially 2'-phenylthiamine are phosphorylated at a greater rate than does the "true" substrate, thiamine, under similar conditions.

Biochemistry, 1976 Sep 21, 15(19), 4185 - 90
Purification of beta-hydroxy-beta-methylglutaryl-coenzyme A reductase from yeast; Qureshi N et al.; Beta-Hydroxy-beta-methylglutaryl-coenzyme A reductase of yeast has been solubilized by two different methods and then purified approximately 5000-fold . The purified enzyme shows a single precipitin band on immunodiffusion, and it moves as a single band of protein and enzyme activity on gel filtration and diethylaminoethylcellulose column chromatography . It also shows one major band on polyacrylamide gel electrophoresis . The specific activity of the pure enzyme is 18 000 to 22 000 nmol of reduced nicotinamide adenine dinucleotide phosphate oxidized per min per mg of protein . The molecular weights of the enzyme, estimated by gel filtration, and the subunits, determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, are 2.6 X 10(5) and 6.0 X 10(4), respectively.

Biochemistry, 1976 Sep 21, 15(19), 4191 - 07
Kinetic analysis of the individual reductive steps catalyzed by beta-hydroxy-beta-methylglutaryl-coenzyme A reductase obtained from yeast; Qureshi N et al.; The mechanism of action of yeast beta-hydroxy-beta-methylglutaryl-coenzyme A reductase has been investigated through kinetic studies on the oxidation of mevaldate by nicotinamide adeninine dinucleotide phosphate (NADP) in the presence of coenzyme A (CoA) and on the reduction of mevaldate by reduced NADP (NADPH) in the absence of presence of CoA or acetyl-CoA . NADP and mevalonate were also used as product inhibitors of the reduction of mevaldate . In the reduction of mevaldate to mevalonate, coenzyme A and acetyl-CoA decreased the Km for mevaldate 30- and 3-fold, respectively . Both compounds increased the Vmax 1.5-fold . These results suggest that CoA is an allosteric activator for the second reductive step and that it acts by enhancing the binding of mevaldate . The intersecting patterns obtained from initial velocities and the patterns produced by product inhibitions suggest the following features of the mechanism . The binding of substrates and release of products proceeds sequentially in both reductive steps, and is ordered throughout or random with respect to the binding of the beta-hydroxy-beta-methylglutaryl-coenzymeA and the first NADPH . The binding of NADPH enhances the binding of the beta-hydroxy-beta-methylglutaryl portion of the CoA ester and the binding of free mevaldate, whereas the binding of NADP leads to an increased affinity of the enzyme for the hemithioacetal (of mevaldate and CoA) and for mevalonate . Thus, the replacement of NADP by NADPH after the first reductive step promotes the conversion of the hemithioacetal to the free carbonyl form, which is then rapidly reduced . The products, CoA and mevalonic acid, of the second reductive step leave the enzyme before the release of the second NADP . This release of the last product is probably the rate-limiting step for the overall process.

Eur J Biochem, 1976 Sep 15, 68(2), 347 - 53
Yeast hexokinase . A fluorescence temperature-jump study of the kinetics of the binding of glucose to the monomer forms of hexokinases P-I and P-II; Hoggett JG et al.; The binding of glucose to the monomeric forms of hexokinases P-I and P-II in Tris and phosphate buffers at pH 8.0 in the presence of 1 mol l-1 KCl has been studied using the fluorescence temperature-jump technique . For both isozymes only one relaxation time was observed; values of tau-1 increased linearly with increasing concentration of free reacting partners . The apparent second-order rate constant for association was about 2 X 10(6) 1 mol-1 s-1 for both isozymes; the differences in the stabilities of the complexes with P-I and P-II are entirely attributable to the fact that glucose dissociates more slowly from its complex with P-I than P-II (approximately 300 s-1 and 1100 s-1 respectively) . Although the kinetic data are compatible with a single-step mechanism for glucose binding the association rate constant was much lower than that expected for a diffusion-limited rate of encounter . Other mechanisms for describing an induced-fit are discussed . It is shown that the data are incompatible with a slow 'prior-isomerization' pathway of substrate binding, but are consistent with a 'substrate-guided' pathway involving isomerization of the enzyme-substrate complex.

Biochim Biophys Acta, 1976 Sep 14, 445(2), 342 - 9
Spectrophotometric pH titrations and nitration with tetranitromethane of the tyrosyl residues in yeast phosphoglycerate kinase; Hjelmgren T et al.; Spectrophotometric pH titrations of phosphoglycerate kinase (EC 2.7.2.3) reveal seven tyrosyl residues . In the native state one tyrosyl residue has pKapp equal to 9.3, another has pKapp of about 12.9, and five have pKapp values close to 11.0 . Titration above pH 10 causes concomitant reduction of the catalytic activity . Reactivation of the enzyme occurs during storage at pH 7.8 . In 6 M guanidine - HCl seven tyrosyl residues with pKapp values equal to 10.0 appear . Nitration of three tyrosyl residues occurs easily when tetranitromethane is used in excess . Four tyrosyl residues appear to be masked or buried . The tyrosyl residue having pKapp equal to 9.3 can be selectively nitrated . Simultaneously the enzyme loses 40% of its catalytic activity . No change in the Km value for one or the other of the two substrates, MgATP or 3-phospho-D-glycerate, was observed in the mononitrated enzyme . On the other hand MgATP protects the tyrosyl residue from nitration whereas 3-phospho-D-glycerate at corresponding condition appears harmless . These results suggest the low ionizing tyrosyl residue to be situated close to the binding site of MgATP, possibly in a pocket just behind . Circular dichroism measurements indicated that minor successive changes occur in the secondary structure, mainly the beta-structure, when the enzyme is being nitrated . It is reasonable to think that these structural changes, possible in combination with steric hindrance, are responsible for the decrease in catalytic activity . Dimerization of the enzyme occurs if the single thiol group is not masked before the tetranitromethane treatment.

C R Acad Sci Hebd Seances Acad Sci D, 1976 Sep 13, 283(4), 417 - 9
{Scanning electron microscopy of different yeast strains and their protoplasts}; Miegeville M et al.; Scanning electron microscopy has been used to study the morphology of seven species of protoplasts from yeasts . In all species examined grooves and droplets were seen advancing with time but their interpretation still remains indefinite.

Biochim Biophys Acta, 1976 Sep 6, 442(3), 275 - 84
Maturation of ribosomes in yeast . II . Position of the low molecular weight rRNA species in the maturation process; Trapman J et al.; Yeast protoplasts were pulse labelled with {5-3H} uridine and the labelling kinetics of the low molecular weight rRNA species were determined in order to gain more insight into the position of those small rRNAs in the process of ribosome maturation . 7-S RNA, the immediate precursor of 5.8-S rRNA, is found to be present only in the nucleus, indicating that the conversion of 7-S to 5.8-S RNA is a nuclear event . 5.8-S rRNA is observed in the cytoplasm almost immediately after its formation . This as well as the presence of only a small amount of 5.8-S RNA in the nucleus, shows that the ribosomal precursor particles of the large ribosomal subunit are very rapidly transported into the cytoplasm once 5.8-S rRNA is formed . Most of the newly synthesized 5-S RNA is found in the nucleus . This nuclear 5-S rRNA is mainly present in the ribosomal precursor particles . However, a small pool of free 5-S rRNA is probably also present.

Biochim Biophys Acta, 1976 Sep 6, 442(3), 265 - 74
Maturation of ribosomes in yeast . I Kinetic analysis by labelling of high molecular weight rRNA species; Trapman J et al.; To study the maturation of ribosomes in Saccharomyces carlsbergensis, protoplasts were pulse labeled with {5-3H}uridine at 15 degrees C . Investigation of the cellular location of pulse-labelled ribosomal RNA precursor and mature ribosomal RNA shows that both the 37-S precursor RNA, common to both 17-S and 26-S rRNA, as well as the 29-S RNA, the direct precursor of 26-S rRNA, are located in the nucleus . Most of the 18-S RNA, the direct precursor of 17-S rRNA, is found in the cytoplasmic fraction . Apart from 37-S and 29-S RNA the nucleus also contains an appreciable amount of 26-S rRNA as well as a small quantity of 18-S RNA . These data indicate that processing of 29-S to 26-S RNA occurs in the nucleus, whereas the conversion of 18-S RNA to 17-S rRNA takes place in the cytoplasm . The kinetics of appearance of pulse-labelled 26-S and 17-S rRNA in the various cytoplasmic ribosomal particles indicate, that newly formed 40-S ribosomal particles are almost immediately incorporated into 80-S ribosomes and polysomes . On the other hand, there appears to exist a fairly large cytoplasmic pool of newly synthesized ribosomal particles containing 26-S rRNA and sedimenting at about 60 S . The kinetics of appearance of newly formed 26-S and 17-S rRNA in mature ribosomes show that the maturation of the large ribosomal subunit takes about twice as much time as that of the small subunit.

Mikrobiologiia, 1976 Sep-Oct, 45(5), 791 - 4
{Growth substance requirements in heterothallic yeast cultures}; Blagodatskaia VM et al.; Vitamin heterotrophy was studied among the following new yeast genera: Leucosporidium, Rhodosporidium and Filobasidium . The requirement in growth factors of various crossing types was compared among these genera and ascomycetens yeast cultures Saccharomycopsis lipolytica and Metschnikowia pulcherrima . Various crossing types of Filobasidium capsuligenum were found to differ in their requirement in growth factors . Various crossing types of Rhodosporidium and Saccharomycopsis lipolytica were stimulated by different growth substances . These characteristics can be used as markers while selecting the types of crossing.

Appl Environ Microbiol, 1976 Sep, 32(3), 320 - 3
An obligate osmophilic yeast from honey; Munitis MT et al.; An obligate osmophilic yeast that requires high sugar concentrations (10 to 20% glucose) for growth was identified as Saccharomyces bisporus var . mellis . Optimum growth for this strain was at 60% glucose . Several non-assimilable compounds permitted growth at glucose concentrations below the minimum requirement and stimulated growth at glucose concentrations above the minimum . No correlation existed between growth stimulation and spheroplast stabilization capacities of the compounds examined.

J Gen Microbiol, 1976 Sep, 96(1), 35 - 50
Cell-wall composition and structure of yeast cells and conjugation tubes of Tremella mesenterica; Reid ID et al.; Cell walls prepared from vegetative yeast cells and from hormone-induced conjugation tubes of the basidiomycete Tremella mesenterica had similar compositions . Evidence was found for 1,3-alpha-glucan (yeast 38%, tube 25%), 1,3-beta-1,6-beta-glucan (yeast 33%, tube 48%) and chitin (both less than 3%) in the walls . The walls also contained xylose (5 to 7%), mannose (6%), glucuronic acid (approx . 2%), and traces of galactose . Protein amounted to less than 2% of the wall weight . The cell capsule was very insoluble and could not be removed from the cell wall . The conjugation hormone did not appear to exert its effect on cell shape by causing gross changes in wall composition.

Infect Immun, 1976 Sep, 14(3), 826 - 31
H and M antigens of Histoplasma capsulatum: preparation of antisera and location of these antigens in yeast-phase cells; Green JH et al.; Antiserum has been prepared in rabbits against the H and M antigens of H . capsulatum with immunoelectrophoretic precipitin arcs used as vaccines . The antiserum is specific for H . capsulatum in the immunodiffusion test and can be used as reference serum for identifying antibodies to these antigens in sera from suspected cases histoplasmosis . We found that (1) hand m antigens are not located on the surface of yeast-phase cells and (ii) complement fixation releases the antigens reactive in the complement fixation test from yeast-phase cells.

Infect Immun, 1976 Sep, 14(3), 623 - 5
Isolation of a purified skin test antigen from Blastomyces dermatitidis yeast-phase cell wall; Lancaster MV et al.; Preparative polyacrylamide gel electrophoresis was used to isolate individual components of an alkaline-soluble-water-soluble fraction of the cell wall of Blastomyces dermatitidis yeast phase . One component isolated demonstrated exceptional specificity and reactivity when tested on guinea pigs infected with B . dermatitidis . This component displayed no cross-reactivity when tested on animals infected with Histoplasma capsulatum . The significance of isolation of a purified, specific antigen is discussed.

Mikrobiologiia, 1976 Sep-Oct, 45(5), 90 - 10
{Conditions of yeast freeze-drying studied by methods of planning experiments}; Fateeva MV et al.; The effect of seven factors on survival and residual humidity of yeast suspensions was studied during freeze-drying of Saccharomyces cerevisiae using methods of mathematical planning of the experiment . A multifactor experiment of the type 2(7-4) was realized, according to which all factors were varied at two levels . Adequate equations for regression were obtained to describe the process in the temperature zone above the eutectic point (from -10 to -15 degrees C) and below it (from -30 to -40 degrees C) . The effect of the studied factors was found to depend on temperature of freeze-drying . The equations were used for optimizing freeze-drying by the method of "sharp ascending".

Mikrobiologiia, 1976 Sep-Oct, 45(5), 781 - 6
{Enzymatic degradation of cell walls of yeast cells at different growth phases}; Tiunova NA et al.; The enzymes of Actinomyces cellulosae were fractionated by precipitation with ammonium sulphate and gel filtration on Sephadex G-75 . Fractionation yielded protease, beta-1,3-glucanase and an enzyme of a low molecular weight and unknown nature involved in lysis by 70% of yeast cells at early exponential growth phase without the participation of the other two enzymes . The protease did not accomplish lysis of the cells; beta-1,3-glucanase was involved in degradation of the cell walls of old yeast cells.

Proc Natl Acad Sci U S A, 1976 Sep, 73(9), 3030 - 4
Circular DNA of a yeast episome with two inverted repeats: structural analysis by a restriction enzyme and electron microscopy; Guerineau M et al.; Small circular DNA molecules from genetically characterized clones of Saccharomyces cerevisiae have been studied by restriction endonuclease analysis and electron microscopy . The circular monomers (6000 bases) are shown to contain two inverted repeats of the same sequence (600 bases) situated opposite each other along the perimeter . Four endonuclease EcoRI fragments are obtained in 1:1:1:1 stoichiometry, and their sum gives a length of about 12,000 bases . The two large fragments and the two small ones differ from each other by 200 bases . We propose a model for the structure of the monomer molecule . Two classes of monomers can be generated by intramolecular recombinations within inverted repeats; they differ by the relative orientation of nonrepeated segments . The structure of dimers as predicted by the model is verified by self-renaturation of single-stranded circles . Inverted repeats in circular molecules may be related to the insertion release faculty of II episome in the chromosomes.

Nucleic Acids Res, 1976 Sep, 3(9), 2379 - 86
Arangement of transfer-RNA -genes in yeast; Feldman H; The redundancy and the arrangement of the genes for specific transfer ribonucleic acids in yeast were studied by the hybridization techniques developed by Birnstiel et al., e.g.{1} . The redundancy was found to be in the order of 10 genes for tRNA1Met, tRNA3Met, tRNA2Ser, and tRNA-Pro . High molecular weight yeast DNA was fractionated by density gradient centrifugation in cesium chloride and the {32p}tRNAs were hybridized to the single fractions . The results together with earlier findings {2} suggest that the cistrons for these tRNAs are arranged in tandem interspersed by 6 to 10 times longer segments of spacer DNA which varies in (G+C) content for the different tRNA species.

Nucleic Acids Res, 1976 Sep, 3(9), 2233 - 41
The kinetics of binding of U-U-C-A to a dodecanucleotide anticodon fragment from yeast tRNA-Phe; Yoon K et al.; The kinetics of U-U-C-A binding to the dodecanucleotide (A-Cm-U-Gm-A-A-Y-A-psi-m5C-U-Gp) isolated from the anticodon region of yeast tRNA-Phe are similar to the kinetics of binding of U-U-C-A to intact tRNA-Phe . A large enhancement in binding constant over that predicted for U-U-C-A-U-G-A-A is observed for both the complexes of dodecanucleotide and tRNA-Phe with U-U-C-A . This strongly suggests that both the anticodon loop in tRNA-Phe and the dodecanucleotide can form four base pairs with U-U-C-A . Furthermore, the enhanced stability cannot be attributed to a special conformation of the anticodon loop, but instead the anticodon loop is probably flexible . A likely explanation for the increased binding is the effect of non-base-paired ends . This increased thermodynamic stability comes from a larger entropy gain rather than a larger enthalpy decrease.

Eur J Biochem, 1976 Sep, 68(1), 209 - 17
The primary structure of a non-initiating methionine-specific tRNA from brewer's yeast; Gruhl H et al.; tRNA3Met, one of the non-initiating methionine-specific tRNAs in brewer's yeast was purified from bulk tRNA labelled with {32P}phosphate by two column chromatographic steps . The primary structure of this tRNA was determined by the usual fingerprinting technique . Analyses of the isolated nucleotides and oligonucleotides from digests with pancreatic and T1 ribonucleases were in good agreement and stated that tRNA3Met consists of 76 nucleotide residues including 13 minor nucleotides . Overlaps from which the complete sequence could be deduced were derived from the analyses of 15 fragments obtained by partial digestion with T1 ribonuclease.

Eur J Biochem, 1976 Sep, 68(1), 199 - 207
DNA-dependent DNA polymerase from yeast mitochondria . Dependence of enzyme activity on conditions of cell growth, and properties of the highly purified polymerase; Wintersberger U et al.; The activity of DNA polymerase was determined in gradient-purified mitochondria from yeast cells grown under a variety of conditions . The specific enzyme activity was found to be dependent on the degree of aeration of the cells, and on the carbon source used for the medium . It was sensitive to glucose repression, and was enhanced about two-fold by the growth of yeast cells in the presence of ethidium bromide . Mitochondria DNA polymerase was highly purified and several properties were determined . Sucrose density gradient centrifugation, and dodecylsulfate-polyacylamide gel electrophoresis revealed the following structure: a monomer of molecular weight around 60 000 aggregated under relatively high salt concentration (0.2 M phosphate buffer) to a dimer of about 120 000 which under low salt concentration (0.2 M Tris-HCl buffer) formed higher aggregates . For optimal activity an Mg2+ ion concentration of 50 mM was found necessary, Mn ions did not promote activity at any concentration tested (0.5--50 mM) . Indeed, if added to Mg2+-containing assays, Mn2+ strongly inhibited enzyme activity at low concentrations . This might be an explanation for the inducation of mitochondrial mutants in yeast cells grown in the presence of Mn2+ ions . Mitochondrial DNA polymerase activity was strongly inhibited by low concentrations of the -SH reagent p-chloromercuribenzoate, the nucleotide analogue cytosine arabinoside triphosphate also exerted an inhibitory effect . An about 50% decrease of activity was observed in the presence of 1 mM o-phenanthroline in assay mixture containing DNA at about the Km concentration . The enzyme preferred a gapped template primer, poly(dA) - (dT)10, over nicked DNA and was unable to use a polyribonucleotide template, poly(rA) - (dT)10 . In the purest preparations no exonuclease activity could be detected.

J Membr Biol, 1976 Aug 26, 28(2-3), 169 - 80
Dielectric properties of yeast cells; Asami K et al.; Dielectric measurements were made on suspensions of intact yeast cells over a frequency range of 10kHz to 100 MHz . The suspensions showed typical dielectric dispersions, which are considered to be caused by the presence of cytoplasmic membranes with sufficiently low conductivity . Since the conductivity of the cell wall was found to be of nearly the same value as that of the suspending medium, composed of Kcl solutions in a range from 10 to 80 mM, the cell wall may be ignored in establishing an electrical model of the cells suspended in such media . An analysis of the dielectric data was carried out by use of Pauly and Schwan's theory . The membrane capacitance was estimated to be 1.1+/-0.1 muF/cm2, which is compared with values reported so far for most biological membranes . The conductivity of the cell interior was almost unchanged with varying KCl concentrations and showed low values owing to the presence of less conducting particles, presumably intracellular organelles . The relatively low dielectric constant of about 50 obtained for the cell interior, in comparison with values of aqueous solutions, may be attributed also to the presence of intracellular organelles and proteins.

Biochim Biophys Acta, 1976 Aug 23, 441(2), 255 - 9
Exchange of phospholipids between mitochondria and microsomes in vitro stimulated by yeast cell cytosol; Cobon GS et al.; Yeast cell cytosol stimulated the exchange of phospholipids between yeast mitochondria and microsomes in vitro, and also between organelles isolated from rat liver . The major phospholipids exchanged in both cases were phosphatidylinositol and phosphatidylcholine, together with smaller amounts of phosphatidylethanolamine . Evidence was also obtained that interconversion of phospholipids occurred during the incubation, probably via base exchange mechanisms.

Biochem J, 1976 Aug 15, 158(2), 255 - 70
The formation of exchangeable sulphite from adenosine 3'-phosphate 5'-sulphatophosphate in yeast; Wilson LG et al.; A new low-molecular-weight bound sulphite was found in yeast enzyme reaction systems which convert the sulphur of 35S-labelled adenosine 3'-phosphate 5'-sulphatophosphate into exchangeable radioactive sulphite . This bound sulphite was separated from other components by paper electrophoresis and Sephadex G-25 chromatography, and shown to be a peptide with multiple thiol groups and an estimated mol.wt . of 1400 . The labelled sulphur in this peptide is highly exchangeable with unlabelled sulphite, but exchangeability decreases with time and freeze-drying . The low-molecular-weight acceptor is tightly bound to enzyme B of the yeast system and, apparently, accepts the sulpho group of adenosine 3'-phosphate 5'-sulphatophosphate and is released as bound sulphite only in the presence of enzymically or chemically reduced fraction C . It is proposed that the low-molecular-weight acceptor is a carrier peptide which, after release of the reduced sulphur, becomes re-oxidized and returns to enzyme B . Fraction C appears to function as an obligatory reductant of the oxidized acceptor before it can accept another-SO-3-moiety from adenosine 3'-phosphate 5'-sulphatophosphate . These findings are consistent with mechanisms proposed for sulphate reduction in spinach and Chlorella, and suggest that fraction C is the natural thiol required in these systems . An improved column technique for the preparation of adenosine 3'-phosphate 5'-sulphatophosphate is described.

Experientia, 1976 Aug 15, 32(8), 998 - 1000
Localization of wheat germ agglutinin receptor sites on yeast cells by scanning electron microscopy; Horisberger M et al.; WGA receptor sites on the surface of Saccharomyces cerevisiae cells pretreated with an alpha-mannanase were localized by gold granules labelled with WGA . The receptor sites were found on the bud scars, the mother cell-bud junction (chitin) and the bud, but not on the mother cell.

Mol Gen Genet, 1976 Aug 2, 146(3), 313 - 5
Yeast cell-cycle mutant cdc21 is a temperature-sensitive thymidylate auxotroph; Game JC; Genetic tests with the yeast cell-cycle mutant cdc21 isolated by Hartwell indicate that the CDC21 gene in yeast is the same as the TMP1 gene, whose mutant alleles confer an auxotrophic requirement for thymidine-5'-monophosphate (dTMP) . Yeast strains carrying cdc21 can grow at 37 degrees in the presence of dTMP provided that they are premeable to this compound . The gene is shown to be linked to ade2 on Chr . XV, and a case of intragenic complementation between cdc21 and another tmp1 allele is reported.

Mol Gen Genet, 1976 Aug 2, 146(3), 253 - 9
The molecular events involved in the induction of petite yeast mutants by fluorinated pyrimidines; Oliver SG et al.; The fluorinated pyrimidines 5-fluorouracil (5FU) and 5-fluorocytosine (5FC) induce the cytoplasmic petite mutation in the yeast Saccharomyces cerevisiae with high efficiency . It was found that in order to induce the mutation, 5FC must first be deaminated to 5FU . However, mutagenesis does not depend on the further conversion of 5FU to its deoxyriboside (5FUDR) and subsequent blockade of intracellular thymidine synthesis, since 5FUDR itself was found not to be mutagenic, and 5FU-induced mutagenesis was not antagonised by supplying thymidine monophosphate (dTMP) to a dTMP permeable strain . In any case, observations of the molecular changes accompanying petite induction in log phase cells ruled out the possibility that mutagenesis resulted simply from the dilution out of replication blocked mitDNA molecules, since the appearance of mutants coincided with the synthesis of altered mitDNA molecules . In different strains, the resulting defective molecules were either maintained, giving rise to suppressive rho- petites, or completely degraded, to give pure clones of neutral rho0 mutants . It is suggested that this degradative process was a conseuqence of the incorporation of 5FU into RNA.

Gann, 1976 Aug, 67(4), 607 - 9
Enhancing effect of a modified yeast mannan on antitumor activity of mitomycin-C; Suzuki M et al.; A synthetic stearolymannan phosphate designated as SMP-Fr . I-d, consisting of three components, fatty acid, polysaccharide, and phosphate, enhanced the therapeutic effect of Mitomycin-C in mice implanted with 1 x 10(7) cells of Ehrlich carcinoma ascites form . Namely, 50% of the mice survived more than 60 days when ineffective doses of 0.5 mg/kg of Mitomycin-C and 50 mg/kg of SMP-Fr . I-d were administered intraperitoneally once daily for 7 days . SMP-Fr . I-d was found to be virtually non-toxic even in a dose of 1,000 mg/kg intraperitoneally in mice.

Genetics, 1976 Aug, 83(4), 675 - 86
Temperature-sensitive yeast mutants defective in meiotic recombination and replication; Roth R; A system is described for isolating temperature-sensitive mutants of Saccharomyces cerevisiae with defects in early meiotic events . We used an otherwise haploid strain disomic (n+1) for chromosome III, and heteroallelic at the leucine-2 locus . Meiotic development was initiated by exposure of the strain to acetate sporulation medium, and monitored by the appearance of leucine-independent intragenic recombinants . Mutant isolation was based on the recovery of thermally induced defects in recombination . The temperature-sensitive characteristic was included to allow eventual characterizations of the temporal period during meiosis when each gene performs its essential function . Following mutagenesis with either ethyl methane sulfonate or nitrosoguanidine individual clones were tested at 34 degrees and 24 degrees for acetate-induced recombination . Starting with 2700 clones, derived from cells that survived mutagenic treatment, we isolated 48 strains with thermally induced lesions in recombination . In the majority of mutants premeiotic replication occurred normally, or nearly normally, at the restrictive temperature, indicating that the meiotic cycle was initiated and that there was a defect in an event required for intragenic recombination . We also detected mutants where the thermally induced lesion in recombination resulted from temperature-sensitive premeiotic DNA synthesis.

Eur J Biochem, 1976 Aug 1, 67(1), 239 - 45
Formation of dolichol monophosphate 2-deoxy-D-glucose and its interference with the glycosylation of mannoproteins in yeast; Lehle L et al.; A crude membrane fraction from Saccharomyces cerevisiae has been found to catalyze 2-deoxy-D-glucose transfer from GDP-2-deoxy-D-glucose to endogeneous lipid and glycoprotein acceptor . Evidence will be represented that the glycolipid formed has properties characteristic dolichol monophosphate 2-deoxy-D-glucose . The 2-deoxy-D-glucosyl group can further be transferred from the glycolipid into a membrane-bound polymer fraction . More than 95% of the radioactivity incorporated can be released by beta-elimination, indicating an O-glycosidic linkage to serine or threonine . The only radioactive product obtained is 2-deoxy-D-glucose . When dolichol monophosphate 2-deoxy-{14C}glucose is incubated together with non-radioactive GDP-mannose subsequent beta-elimination yields no higher oligosaccharides in contrast to an experiment where dolichol monophosphate {14C}mannose and GDP-mannose are used as donors . The results are consistent with the assumption that the non-physiological nucleotide sugar interferes with GDP-mannose for mannosylation and terminates further elongation of the serine/threonine-bound oligomannose side chains . UDP-2-deoxy-D-glucose, used as donor, results also in the formation of a glycolipid . In this case, however, no polyprenol derivative is formed . Instead, the glycolipid displays properties characteristic of sphingolipid or a sterol glucoside.

Arch Microbiol, 1976 Aug, 109(1-2), 115 - 8
Asymmetric distribution of concanavalin A binding sites on yeast plasmalemma and vacuolar membrane; Boller T et al.; Isolated vacuoles of Saccharomyces cerevisiae did not bind Concanavalin A (labelled with tritium or with a fluorescent dye) unless the vacuoles were rendered permeable and their inner membrane surface made accessible . Yeast protoplasts, on the other hand, bound large amounts of Concanavalin A on their surface, and the number of binding sites was not increased after a gentle lysis expected to expose also the inner surface of the plasmalemma . It is concluded that both the plasmalemma and the vacuolar membrane carry Concanavalin A binding sites exclusively on the surface opposite to the cytoplasmic matrix.

Z Parasitenkd, 1976 Jul 27, 50(1), 73 - 9
Studies on Hymenolepis microstoma in vitro . II . Effect of yeast extract on development and maturation; Khan ZI et al.; Four day old in vivo Hymenolepis microstoma were cultured in vitro for 6 days in media containing 2, 1, 0.5 and 0.1% yeast extract . Worms from all groups including control group increased in length and produced nearly equivalent numbers of proglottids . However, worms grown in yeast extract added media produced significantly more mature proglottids and were heavier than those in the control medium . The possibility of pyridoxin involvement has been contemplated . Effects of osmotic pressure and pH on the development of worms are discussed.

C R Acad Sci Hebd Seances Acad Sci D, 1976 Jul 19, 283(3), 275 - 7
{Radiorestoration by 3 cytokinins contained in yeast RNAs and extracts, of scorzonera tumor tissues exposed to cobalt-60 gamma rays}; Jonard R et al.; The 3 natural cytokinins contained both in the extracts and RNA of yeast and the tumor tissues cultivated in vitro, elicit radiorestorative properties from the crown-gall tissues of Scorsonera submitted to Co60 gamma-rays . However the cytokinins produce no stimulating effect whatsoever on the non irradiated tissues that are nontheless highly stimulated by yeast extract and their RNA.

Biochemistry, 1976 Jul 13, 15(14), 3046 - 51
Structural analysis of O2'-methyl-5-carbamoylmethyluridine, a newly discovered constituent of yeast transfer RNA; Gray MW; A compound tentatively identified as O2-methyl-5-carboxymethyluridine (cm5Um) was recently isolated in this laboratory from bulk yeast transfer RNA (Gray, M . W . (1975), Can, J . Biochem . 53, 735-746) . Alkaline hydrolysis of yeast tRNA releases this nucleoside as part of an alkali-stable dinucleotide, cm5Um-Ap, from which sufficient cm5Um was prepared in the present investigation for a detailed examination of its properties . The ultraviolet absorption spectra and chromatographic and electrophoretic properties of cm5Um were consistent with the proposed structure, which was confirmed by characterization of the base and sugar moieties as 5-carboxymethyluracil and 2-O-methylribose, respectively . Snake venom hydrolysis of yeast tRNA releases cm5Um in the form of a carboxyl-blocked 5'-nucleotide, designated pU-2 . Identification of the alkali-labile blocking group in pU-2 as an amide was based on quantitative assay for ammonia released upon acid hydrolysis of the corresponding nucleoside, U-2, and by chromatographic comparison of U-2 with the semisynthetic methyl ester and amide derivatives of cm5Um (mcm5Um and ncm5Um, respectively) . Quantitative analysis has indicated that ncm5Um may be confined to a single species of yeast tRNA . In view of the unique localization (the "Wobble" position of the anticodon sequence) and coding properties (pairing with A but not with G) of other cm5U derivatives in transfer RNA, the dinucleotide cm5Um-Ap may be derived from the first two positions of the anticodon sequence of a yeast tRNA species recognizing an NUA codon . This predicts that O2-methyl-5-carbamoylmethyluridine will be found in an isoleucine, leucine, or valine isoacceptor.

Prikl Biokhim Mikrobiol, 1976 Jul-Aug, 12(4), 548 - 51
{Elimination of phenylalanine from amino acid mixtures obtained from yeast hydrolysates and autolyzates}; Belikov VM et al.; In order to obtain amino acid mixtures devoid of phenylalanine, adsorption of aromatic amino acids was studied during their chromatography on ion-exchange resin IA-Ip . When 40 g of the amino acid mixture were passed through 400 ml of the swollen ion-exchange resin, phenylalanine and tyrosine were eliminated and 67% of dry substance were yielded . Ion-exchange resin adsorbed phenylalanine and tyrosine could be regenerated . The use IA-Ip is advantageous as compared with that of ion-exchange resin Amberlite IR-45 and activated charcoal.

Can J Microbiol, 1976 Jul, 22(7), 960 - 6
Conjugation in the yeast Guilliermondella selenospora Nadson et Krassilnikov; Kreger-van Rij NJ et al.; Conjugation in Guilliermondella selenospora took place via conjugation tubes from cells in different hyphae . Afterwards, a septum was formed in the channel connecting the two cells which turned into asci or formed buds which became asci . Conjugation between adjacent hyphal cells was also found . Cell contact without fusion with denticles and stalks, which occurs in G . selenospora, was compared with conjugation.

Can J Microbiol, 1976 Jul, 22(7), 989 - 95
A modified procedure for studying enzyme secretion in yeast sphaeroplasts: subcellular distribution of invertase; Holbein BE et al.; A significantly modified procedure for investigating enzyme secretion from yeast sphaeroplasts, and results from its application are described . Sphaeroplasts were derepressed for invertase biosynthesis in the presence of helicase and fractionated to reveal the distribution of high and low molecular weight forms of invertase . Secreted enzyme was found to be of high molecular weight, exclusively . Less than 10% of the total invertase activity was present in washed sphaeroplasts and of this, 43% was soluble, consisting of both high and low molecular weight forms of invertase . Washed membranes retained 32% of the internal invertase activity, and on solubilization with Triton X-100 the enzyme was found to be of an intermediate molecular weight . These results are consistent with the hypothesis that invertase is glycosylated at the plasma membrane.

J Gen Microbiol, 1976 Jul, 95(1), 27 - 30
Phytochrome system of the yeast Candida guilliermondii and recovery from ultraviolet injury; Fraikin GY et al.; The effect of red (660 nm) and far-red (730 nm) light on the stability of the yeast Candida guilliermondii to lethal u.v . radiation has been studied . Reactivation and protection were exhibited for 30 min after treatment with red light and were abolished by far-red exposure applied within this time period . The temperature dependence of the reactivation effect was also studied . The data obtained showed that the properties of recovery and protection against u.v . exposure are associated with the phytochrome system of the yeast.

Lepr India, 1976 Jul, 48(3), 268 - 71
Hyaluronic acid and yeast extract do not oxidize DOPA; Prabhakaran K; Hyaluronic acid and yeast extract, separately and in combination, were tested for their ability to oxidize dopa to pigment . Two types of hyaluronic acid and yeast extract were used . The activities were assayed both spectrophotometrically and by oxygen-uptake determinations . The results were uniformly negative . The biological role of hyaluronic acid is discussed . Use of pigment formation from phenolic compounds as an identification test of another organism is pointed out.

Prikl Biokhim Mikrobiol, 1976 Jul-Aug, 12(4), 619 - 21
{Method of arrest and fixation of growth of yeast cultures in the postincubation period}; Smashevskii ND; In order to arrest the growth and to fix yeast cultures during the postincubation period on natural and synthetic nutrient media, 10% oxalic acid can be used . The fixative is used at a concentration of 0.025 and 0.05 ml/l . Therefore, it induces on noticeable dilution of the suspension and allows precise measurements of the yeast weight.

Biofizika, 1976 Jul-Aug, 21(4), 752 - 4
{Effect of yeast cell membrane components on the IR spectrum of the cell}; Guliaeva ND et al.; IR-technique was used to study the effect of yeast cells treatment by water-alcohols mixtures on the quantitative relationship between the intensities of different bands in the spectra . The analysis of spectra made it possible to suggest that the reflection of the IR-irradiation from the cell is governed by the nucleoprotein layer of its envelope . It is shown that the treatment of yeast cell with ribonuclease raises the "IR-permeability" of the cell envelope.

J Bacteriol, 1976 Jul, 127(1), 354 - 61
Bromodeoxyuridine 5'-monophosphate incorporation into yeast nuclear and mitochondrial deoxyribonucleic acid; Leff J et al.; Standard laboratory yeast strains can be enriched for thymidine 5'-monophosphate (TMP) uptake derivatives that generate only a low percentage of respiratory-deficient colonies (petites) under inhibition of TMP biosynthesis . Such mutants incorporated bromodeoxyuridine 5'-monophosphate (BrdUMP) into both nuclear and mitochondrial deoxyribonucleic acid (mtDNA); however, they showed a selectivity for TMP over BrdUMP incorporation . The preferential incorporation of {3H}TMP or BrdUMP into mtDNA was strain dependent . The density increments after growth in the presence of BrdUMP reached 50 mg/ml for nuclear DNA and 22 mg/ml for mtDNA in CsCl gradients . Density shifts corresponding to 4% bromouracil substitution were easily detected . Preliminary density transfer experiments confirm that mtDNA does not replicate in synchrony with nuclear DNA.

Biochem J, 1976 Jul 1, 157(1), 15 - 22
Kinetics and reaction mechanism of yeast alcohol dehydrogenase with long-chain primary alcohols; Schopp W et al.; Kinetic studies of yeast alcohol dehydrogenase with NAD+ and ethanol, hexanol or decanol as substrates invariably result in non-linear Lineweaver-Burk plots if the alcohol is the variable substrate . The kinetic coefficients determined from secondary plots are consistent with an 'equilibrium random-order' mechanism for extremely low alcohol concentrations and for all alcohols, the transformation of the ternary complexes being the rate-limiting step of the reaction . This mechanism also applies to long-chain substrates at high concentrations, whereas the rate of the ethanol-NAD+ reaction at high ethanol concentrations is determined by the dissociation of the enzyme-NADH complex . The dissociation constants for the enzyme-NAD+ complex and for the enzyme-alcohol complexes obtained from the kinetic quotients satisfactorily correspond to the dissociation constants obtained by use of other techniques . It is suggested that the non-linear curves may be attributed to a structural change in the enzyme itself, caused by the alcohol.

Eur J Biochem, 1976 Jul 1, 66(2), 277 - 84
Spectroscopic investigation of binary and ternary coenzyme complexes of yeast alcohol dehydrogenase; Karlovic D et al.; Corrected fluorescence properties of yeast alcohol dehydrogenase and its coenzyme complexes have been investigated as a function of temperature . Dissociation constants have been obtained for binary and ternary complexes of NAD and NADH by following the enhancement of NADH fluorescence or the quenching of the protein fluorescence . It is found that the presence of pyrazole increases the affinity of NAD to the enzyme approximately 100-fold . The formation of the ternary enzyme - NAD - pyrazole complex is accompanied by a large change in the ultraviolet absorption properties, with a new band in the 290-nm region . Significant optical changes also accompany the formation of the ternary enzyme-NADH-acetamide complex . The possible origin for the quenching of the protein fluorescence upon coenzyme binding is discussed, and it is suggested that a coenzyme-induced conformational change can cause it . Thermodynamic parameters associated with NAD and NADH binding have been evaluated on the basis of the change of the dissociation constants with temperature . Optical and thermodynamic properties of binary and ternary complexes of yeast alcohol dehydrogenase are compared with the analogous properties of horse liver alcohol dehydrogenase.

J Biol Chem, 1976 Jun 25, 251(12), 3545 - 52
Yeast alpha-isopropylmalate isomerase . Factors affecting stability and enzyme activity; Bigelis R et al.; Yeast alpha-isopropylmalate isomerase was found to be markedly stabilized by high concentrations of glycerol and (NH4)2SO4 . Such conditions of high ionic strength inhibited the enzyme, stabilized the enzyme to heat, and affected kinetic parameters . The isomerase was found to exhibit ionic strength-dependent hysteresis when enzyme, totally but reversibly inhibited by storage under conditions of high ionic strength of (NH4)2SO4, was transferred to a lower concentration of (NH4)2SO4 . Alpha-Isopropylmalate isomerase was found to be sensitive to KCN and certain other chelators . The inactivation by KCN was prevented by high concentrations of (NH4)2SO4 . These observations implicated a metal involvement but the nature of the metal was not revealed . The metal involvement and some of the other properties of alpha-isopropylmalate isomerase reveal a similarity to aconitase . The similarities in properties between the isomerase and aconitase are summarized . Studies of yeast alpha-isopropylmalate isomerase indicated that it is a single polypeptide of about Mr = 90,000.

Eur J Biochem, 1976 Jun 15, 66(1), 65 - 77
Yeast hexokinase: substrate-induced association--dissociation reactions in the binding of glucose to hexokinase P-II; Hoggett JG et al.; A method is described for the purification of native hexokinases P-I and P-II from yeast using preparative isoelectric focussing to separate the isozymes . The binding of glucose to hexokinase P-II, and the effect of this on the monomer--dimer association--dissociation reaction have been investigated quantitatively by a combination of titrations of intrinsic protein fluorescence and equilibrium ultracentrifugation . Association constants for the monomer-dimer reaction decreased with increasing pH, ionic strength and concentration of glucose . Saturating concentrations of glucose did not bring about complete dissociation of the enzyme showing that both sites were occupired in the dimer . At pH 8.0 and high ionic strength, where the enzyme existed as monomer, the dissociation constant of the enzyme-glucose complex was 3 X 10(-4) mol 1(-1) and was independent of the concentration of enzyme . Binding to the dimeric form at low pH and ionic strength (I=0.02 mol 1(-1), pH less than 7.5) was also independent of enzyme concentration (in the range 10-1000 mug ml-1) but was much weaker . The process could be described by a single dissociation constant, showing that the two available sites on the dimer were equivalent and non-cooperative; values of the intrinsic dissociation constant varied from 2.5 X 10(-3) mol 1(-1) at pH 7.0 to 6 X 10(-3) at pH 6.5 . Under intermediate conditions (pH 7.0, ionic strength=0.15 mol 1(-1)), where monomer and dimer coexisted, the binding of glucose showed weak positive cooperatively (Hill coefficient 1.2); in addition, the binding was dependent upon the concentration of enzyme in the direction of stronger binding at lower concentrations . The results show that the phenomenon of half-sites reactivity observed in the binding of glucose to crystalline hexokinase P-II does not occur in solution; the simplest explanation of our finding the two sites to be equivalent is that the dimer results from the homologous association of two identical subunits.

J Biol Chem, 1976 Jun 10, 251(11), 3221 - 8
Transport of riboflavin into yeast cells; Perl M et al.; Riboflavin-requiring mutants of Saccharomyces cerevisiae are able to transport 14C-labeled riboflavin into the cell, although no significant transport is seen in commercial yeast or in the parent strain from which the mutants were derived . Transport activity is greatest in the early to mid-log phase of anaerobic growth and declines sharply in the late log phase . In aerobically grown cells activity is substantially lower at all stages of growth . In the assay devised for its measurement, transport activity shows a sharp pH optimum at pH 7.5, a strong temperature dependence (EA = 23,100 cal/mol), and saturation kinetics with respect to riboflavin (Km = 15 muM), characteristics consistent with a carrier-mediated mechanism . Monovalent inorganic cations, particularly K+ and Rb+, stimulate riboflavin uptake, while certain organic cations are inhibitory . Besides riboflavin only 7-methylriboflavin, 8-methylriboflavin, and 5-deazaflavin have been found to serve as substrates, while lumiflavin, tetraacetylriboflavin, and N10-{4'-carboxybutyl}-7,8-dimethylisoalloxazine do not, although a number of flavin analogs in which the ribityl side chain is modified are good competitive inhibitors of riboflavin uptake . Compounds resembling the ribityl side chain, such as sugars and sugar alcohols, do not inhibit . An apparent inhibition of uptake by D-glucose, D-mannose, and D-fructose, which develops in the course of assay, proved to result from stimulation of an opposing process, the release of riboflavin from the cells.

Biochim Biophys Acta, 1976 Jun 7, 438(1), 119 - 30
The proton transfer reactions catalyzed by yeast pyruvate kinase; Ford SR et al.; 1 . The proton-transfer reactions of yeast pyruvate kinase (EC 2.7.1.40) were studied . Proton-transfer from C-3 of phosphoenolpyruvate to water occurs only in the presence of the phosphoryl-acceptor ADP . Proton transfer from C-3 of pyruvate to water occurs only in the presence of ATP . However, the proton transfer in the latter case occurs 10-100 times faster than phosphoryl transfer; this supports a mechanism in which proton transfer precedes phosphoryl transfer in the reverse reaction of pyruvate kinase . 2 . The characteristics of proton-transfer reactions of yeast pyruvate kinase were compared with those previously reported for rabbit muscle pyruvate kinase (Robinson, JL . and Rose, I.A . (1972) J . Biol . Chem . 247, 1096-1105) . The pH-profiles and the divalent cation dependencies were similar for Fru-1,6-P2-activated yeast pyruvate kinase and the muscle enzyme . Pyruvate enolization by yeast pyruvate kinase has an absolute requirement for ATP in contrast to enolization by the muscle enzyme which proceeds when ATP is replaced by Pi or other dianions . 3 . Fructose-1,6-bisphosphate was shown to affect the catelytic steps of yeast pyruvate kinase in addition to the binding of substrates . Its role depends on the divalent cation used to activate the enzyme.

Biochim Biophys Acta, 1976 Jun 7, 438(1), 108 - 18
Secondary kinase reactions catalyzed by yeast pyruvate kinase; Leblond DJ et al.; 1 . Yeast pyruvate kinase (EC 2.7.1.40) catalyzes, in addition to the primary, physiologically important reaction, three secondary kinase reactions, the ATP-dependent phosphorylations of fluoride (fluorokinase), hydroxylamine (hydroxylamine kinase) and glycolate (glycolate kinase) . 2 . These reactions are accelerated by fructose-1,6-bisphosphate, the allosteric activator of the primary reaction . Wth Mg2+ as the required divalent cation, none of these reactions are observed in the absence of fructose-biphosphate . With Mn2+, fructose-bisphosphate is required for the glycolate kinase reaction, but merely stimulates the other reactions . 3 . The effect of other divalent cations and pH on three secondary kinase reactions was also examined . 4 . Results are compared with those obtained from muscle pyruvate kinase and the implications of the results for the mechanism of the yeast enzyme are discussed.

Carbohydr Res, 1976 Jun, 48(2), 225 - 37
Methylation and acetolysis of extracellular D-mannans from yeast; Seymour FR et al.; Methylation-fragmentation analyses were conducted on a series of extra-cellular, yeast alpha-D-linked mannans representing six different structural types . D-Mannans of low degree of branching were produced by Hansenula capsulata strains and by species related to H . holstii, The former consisted primarily of (1 leads to 2)- and (1 leads to 6)-linked D-mannosyl residues; the latter, of (1 leads to 2)- and (1 leads to 3)-linked D-mannosyl residues . Although the remaining structural types were highly branched, each gave distinct methylation-patterns indicative of (1 leads to 6)-linked backbones to which are appended non-(1 leads to 6)-linked side-chains . Acetolysis studies were correlated with the methylation analyses, and the correlation demonstrated that each branched polymer possesses side chains of heterogeneous length.

Biochem J, 1976 Jun 1, 155(3), 661 - 7
Dissociation and catalysis in yeast hexokinase A; Williams DC et al.; 1 . The specific activity of yeast hexokinase A depends on the concentration of the protein in the solution being assayed . When a solution containing 13.5 mg of hexokinase A/ml is diluted 10--100-fold at various values of pH and temperature, there is a gradual decline in the specific activity of the enzyme until an equilibrium value is reached, which varies with the chosen experimental conditions . 2 . The catalytic activity lost when hexokinase A (1 mg/ml) is incubated at 30degreesC is recovered by lowering the temperature to 25degreesC . 3 . These concentration- and temperature-dependent phenomena are consistent with the existence of a monomer-dimer equilibrium in which the dimer alone is the catalytic form of the enzyme . 4 . Glucose alone prevents the decline in specific activity of hexokinase A after dilution, but it does not re-activate dilute solutions solutions of the enzyme . It is concluded that glucose binds to both the dimer and the monomer and prevents both association and dissociation . 5 . The progress curve describing the phosphorylation of glucose catalysed by hexokinase A does not attain a steady state . It is possible that dissociation of catalytically active dimers in a ternary complex with glucose and ATP (or glucose 6-phosphate and ADP) could explain the non-linearity of this progress curve.

Steroids, 1976 Jun, 27(6), 821 - 9
Lanosterol 14alpha-demethylase . Similarity of the enzyme system from yeast and rat liver; Mitropoulos KA et al.; The chemical synthesis of 24,25-dihydro{32-14C}lanosterol is described . The incubation of this material with a cell-free system from Saccharomyces cerevisiae or with a microsomal preparation from rat liver resulted in both cases in the release of {14C}formic acid . This result suggests that in the biosynthesis of ergosterol in yeast, as well as in that of cholesterol in higher animals, the 14alpha-methyl group of lanosterol is removed as formic acid . In both systems, the measurement of the rate of release of {14C}formic acid from 24,25-dihydro{32-14C}lanosterol provides a simple and direct assay of lanosterol 14alpha-demethylase . Carbon monoxide inhibited both yeast and liver 14alpha-demethylase.

Eur J Biochem, 1976 Jun 1, 65(2), 543 - 52
Two forms of RNA polymerase B in yeast . Proteolytic conversion in vitro of enzyme BI into BII; Dezelee S et al.; Special care to prevent proteolysis during yeast RNA polymerase B purification leads to the appearance of two forms of enzymes, BI and BII, with different molecular weight (465 000) and 435 000, respectively) . The two forms of enzyme can be separated by ion-exchange chromatography or polyacrylamide gel electrophoresis . Their subunit structures were compared by sodium dodecylsulfate gel electrophoresis, the only observed difference between the two enzymes is in the molecular weight of the heaviest subunit which is 220 000 for enzyme BI and 180 000 for enzyme BII . Otherwise, the two enzymes have seven common subunits of molecular weights 150 000, 45 000, 26 000, 22 500, 14 500, 12 500 and 9000 . Two additional polypeptide chains of 32 000 and 16 500 Mr are dissociated from the enzyme upon polyacrylamide gel electrophoresis or DEAE Sephadex chromatography . The largest subunit of enzyme BI (Mr 220 000) can be specifically cleaved in vitro by a yeast protease extract, generating a polypeptide chain indistinguishable from the largest subunit of enzyme BII . This proteolytic cleavage of enzyme BI in vitro is inhibited by phenylmethylsulfonyl fluoride and does not significantly change the activity of the enzyme with single-stranded or double-stranded DNA as template . The precursor-product relationship of the different forms of class B RNA polymerases in eukaryotic cells is discussed.

Proc Natl Acad Sci U S A, 1976 Jun, 73(6), 2082 - 5
Biogenesis of mitochondria: molecular mapping of the mitochondrial genome of yeast; Linnane AW et al.; We have developed a new procedure for the detailed molecular mapping of any allele of the yeast (Saccharomyces cerevisiae) mitochondrial genome . The procedure employs a collection of different genetically characterized petite strains whose genomes have been physically defined by molecular hybridization . The map position of an allele is within the DNA segment common to all defined petites that can be shown by marker rescue to retain the locus . The same collection of petites can be used to locate the positions of mitochondrial rRNA and tRNA cistrons and DNA fragments produced by restriction endonucleases.

Proc Natl Acad Sci U S A, 1976 Jun, 73(6), 1863 - 7
Synthesis of yeast histones in the cell cycle; Moll R et al.; The yeast, Saccharomyces cerevisiae, contains four types of histones resembling histones H3, H2b, H2a, and H4 of animal cells . These proteins are synthesized primarily, if not exclusively, in the S-phase of the cell cycle . This result is discussed with reference to the insensitivity of ongoing DNA replication in yeast to inhibitors of protein synthesis.

J Hyg (Lond), 1976 Jun, 76(3), 349 - 53
The laboratory evaluation of iodophor disinfectants with yeast suspensions; Charley CM et al.; The report investigates the variation in results noticed when testing iodophor disinfectants in the presence of a 5% (w/v) yeast suspension . It was found that these variations were not related to individual iodophor formulations but bore a direct relationship with the storage time of the prepared yeast suspension.

J Cell Biol, 1976 Jun, 69(3), 717 - 21
A highly ordered ring of membrane-associated filaments in budding yeast; Byers B et al.; In Saccharomyces cerevisiae, a highly ordered ring of 10-nm filaments is intimately associated with the plasma membrane within the neck of the bud . The ring is formed during early bud emergence and disappears when cytokinesis begins.

Biotechnol Bioeng, 1976 Jun, 18(6), 791 - 804
Yield and maintenance relations of yeast growth in the chemostat at superoptimal temperatures; Van Uden N et al.; A model is proposed that accounts for the decreases in yield which occur in chemostat cultures of mesophilic yeasts at superoptimal growth temperatures . Two yield depressing effects were identified, one due to increased maintenance requirements by the viable fraction of the population, the other due to energy substrate dissipation by the nonviable function . The two effects are functions of the dilution rate, as is the fraction of nonviable cells . Experimental results were obtained on the yield, maintenance, and dissipation of energy substrate in a glucose-limited chemostat culture of a respiration-deficient mutant of Saccharomyces cerevisiae at 39 degrees C . The rates of glucose utilization for maintenance and for dissipation constituted, respectively, 33-28% and 15-9% of the total glucose utilization rate over the range of dilution rates tested (0.038-0.064 hr-1), while the yield varied over this range from 0.066-0.085 g of biomass (dry wt) per gram of glucose.

Biophys J, 1976 Jun, 16(6), 641 - 53
Changes in the restriction of molecular rotational diffusion of water-soluble spin labels during fatty acid starvation of yeast; Henry SA et al.; Yeast mutants lacking fatty acid synthetase activity (fas-) die when deprived of saturated fatty acid under conditions which are otherwise growth-supporting . The spin label technique is used to show that restriction of molecular rotational diffusion of spin label molecules dissolved in aqueous zones increases several fold under conditions of fatty acid starvation while the apparent physical state of cellular hydrocarbon zones remains essentially unchanged . We focus attention on the cellular aqueous interior as the potential site of alteration under selective starvation conditions . Correspondences exist between restriction of molecular motion of water soluble spin labels dissolved in the cell and loss of cell viability . The correspondences to changes in the molecular motion of hydrocarbon soluble spin labels are much less or are not detectable.

Biochem J, 1976 Jun 1, 155(3), 721 - 3
Differences in the degradation of yeast phosphofructokinase by proteinases A and B from yeast; Huse K et al.; Proteinase A from yeast causes a stepwise degradation of yeast phosphofructokinase, resembling the action of subtilisin on this enzyme . Proteinase B, however, exhibits a limited proteolysis similar to the action of alpha-chymotrypsin.

Biochim Biophys Acta, 1976 May 28, 428(3), 583 - 90
Biosynthesis of yeast mannan . Independent formation of two carbohydrate moieties in the mannoprotein molecule; Farkas V et al.; The formation of two distinct types of carbohydrates moieties, beta-elminable saccharides attached to serine and/or threonine and of the polysaccharide portion of yeast mannan-protein was investigated using the particulate mannan synthetase from Saccharomcyes cerevisiae and GDP-{U-14C}mannose as mannosyl donor . The accumulated evidence obtained by following the kinetics of mannose incorporation into the different carbohydrate portions of mannoprotein, kinetics of thermal denaturation of enzymes responsible for their synthesis and by "pulse-chase" experiment where the change in the distribution of incorporated radioactivity was followed between the two carbohydrate moieties strongly suggests that the two carbohydrate portions in yeast mannoprotein are being synthesized independently, most probably by different sets of enzymes . At the same time, the obtained data show the beta-eliminable saccharides attached to serine and threonine in the peptide do not serve as precursors in the formation of polysaccharide part of mannoprotein.

Biochim Biophys Acta, 1976 May 28, 428(3), 573 - 82
Biosynthesis of yeast mannan . Diversity of mannosyltransferases in the mannan-synthesizing enzyme system from yeast; Farkas V et al.; 1 . A microsomal enzyme preparation from the yeast Saccharomyces cerevisiae catalyzes the transfer of mannosyl units from GDPmannose to mannose and a number of mannose-containing oligosaccharides and glycosides whereby different glycosidic bonds are formed . 2 . Of the compounds tested besides mannose, only those containing an alpha-linked mannosyl unit at the nonreducing position of their molecule were effective as acceptors . Monodeoxyanalogues of mannose as well as alpha-mannose phosphates did not serve as acceptors in the above reaction . 3 . The structure of the product formed with mannose as acceptor was determined to be O-alpha-D-mannosyl-(1 leads to 2)-mannose; with alphaMan (1 leads to 6)mannose as the acceptor, the product was alphaMan(1 leads to 6)mannose and with alphaMan-(1 leads to 2)mannose the product was tentatively characterized as a mixture of alphaMan-(1 leads to 3)alphaMan(1 leads to 2)mannose and alphaMan(1 leads to 2)alphaMan(1 leads to 2)mannose . 4 . The enzymes catalyzing the formation of different types of glycosidic bonds differed in their acceptor specificity, pH-activity curves and rates of heat denaturation . 5 . Radioactive disaccharides were unable to enter the mannan protein molecule in the cell-free system while free radioactive mannose did incorporate into polysaccharide to a minor extent under the same conditions.

J Biol Chem, 1976 May 25, 251(10), 2898 - 904
Methylated, blocked 5' termini of yeast mRNA; Sripati CE et al.; mRNAs of the yeast, Saccharomyces cerevisiae, have modified 5' termini similar but not identical with those present in the higher eukaryotes . Poly(A)-containing RNA isolated from spheroplasts or from polysomes of cells labeled with {methyl-3H}methoionine or 32Pi contain methylated, blocked 5'-terminal structures of composition: m7G(5')pppAp and m7G(5')pppGp, occurring in a relative distribution of 75% and 25%, respectively . Furthermore there is no N6-methyladenosine nor any other methylated nucleoside in the entire molecule of poly(A)-containing RNA . Experiments with a mutant, temperature-sensitive for the transport of mRNA to cytoplasm, suggest that the methylation and addition of the blocking group take place in the nucleus and that the genetic lesion in the mutant does not affect these mechanisms.

Biochim Biophys Acta, 1976 May 21, 433(3), 583 - 96
Sugar transport and potassium permeability in yeast plasma membrane vesicles; Fuhrmann GF et al.; Plasma membrane vesicles were isolated from homogenised yeast cells by filtration, differential centrifugation and aggregation of the mitochondrial vesicles at pH 4 . As judged by biochemical, cell electrophoretic and electron microscopic criteria a pure plasma membrane vesicle preparation was obtained . The surface charge density of the plasma membrane vesicles is similar to that of intact yeast cells with an isoelectric point below pH 3 . The mitochondrial vesicles have a higher negative surface charge density in the alkaline pH range . Their isoelectric point is near pH 4.5, where aggregation is maximal . The yield of vesicles sealed to K+ was maximal at pH 4 and accounted for about one third of the total vesicle volume . The plasma membrane vesicles demonstrate osmotic behaviour, they shrink in NaCl solutions when loosing K+ . As in intact yeast cells the entry and exit of sugars like glucose or galactose in plasma membrane vesicles is inhibited by UO22+ . Counter transport in plasma membrane vesicles with glucose and mannose and iso-counter transport with glucose suggests that a mobile carrier for sugar transport exists in the plasma membrane . After galactose pathway induction in the yeast cells and subsequent preparation of plasma membrane vesicles the uptake of galactose into the vesicles increased by almost 100% over the control value without galactose induction . This increase is explained by the formation of a specific galactose carrier in the plasma membrane.

Biochemistry, 1976 May 18, 15(10), 2172 - 7
Physicochemical and kinetic properties of iodinated yeast 3-phosphoglycerate kinase; Roustan C et al.; The present studies have established that there is a critical tyrosyl residue in yeast 3-phosphoglycerate kinase . The iodination of this enzyme results in an inactivation following first-order kinetics . The extent of the modification is limited to only one tyrosyl residue . The monoiodotyrosine formation which leads to inactivation of the enzyme does not induce any significant conformational change as evidenced by hydrogen exchange and optical rotatory dispersion . The role of this tyrosine in the action of the yeast 3-phosphoglycerate kinase is studied . An effective protection against inactivation is observed with 3-phosphoglycerate, and the characteristic spectral effect of 3-phosphoglycerate binding cannot be detected in the modified enzyme . It is concluded that the essential tyrosyl residue may play a role in substrate binding.

Biochemistry, 1976 May 18, 15(10), 2082 - 6
Control of ribonucleic acid synthesis in eukaryotes . 3 . The effect of cycloheximide and edeine on rna synthesis in yeast; Gross KJ et al.; The addition of cycloheximide to a thermosensitive conditional yeast mutant (ts-187) before and after transfer to the nonpermissive temperature (36 degrees C) for initiation of protein synthesis produces the uncoupling of the RNA and protein synthetic machineries . Since the drug can produce this relaxation in the presence and absence of protein synthesis, it is concluded that the coupling of protein and RNA synthesis, which a temperature shift produces, is not exclusively related to the inhibition of protein synthesis . Support for this assumption has been obtained using the parental (A364A) strain . Transferring this strain to 36 degrees C produces inhibition of RNA synthesis in the presence of stimulation of protein synthesis . Furthermore, cycloheximide and edeine prevent this inhibtion of RNA synthesis that temperature shift produces . It is, therefore, postulated that this inhibition of RNA synthesis results from the synthesis or activation of a factor(s) elicited by the increase in temperature whose function is to repress the transcriptional apparatus . Cycloheximide or edeine can prevent the function of this repressor-like factor by binding to the factor or by preventing its synthesis . The fact that inhibition of protein synthesis either by cycloheximide action or temperature shift in ts-187 produces inhibition of RNA synthesis in isolated nuclei indicates that, in addition to the aforementioned repressor, other factor(s) having a promoter function may exist . Since a slight inhibition of protein synthesis produces nuclear template restrictions, it is postulated that the promoter-like factor(s) is a polypeptide different from the RNA polymerase and, at least in yeast, has a high turnover.

Biochemistry, 1976 May 18, 15(10), 2070 - 2081
Control of ribonucleic acid synthesis in eukaryotes . 2 . The effect of protein synthesis on the activities of nuclear and total DNA-dependent RNA polymerase in yeast; Gross KJ et al.; A thermosensitive conditional yeast mutant (ts-187) which suppresses protein synthesis at the nonpermissive temperature (36 degrees C) also suppresses RNA synthesis . The effect of temperature on the mutant is similar to the addition of cycloheximide--it inhibits the incorporation of labeled precursors into RNA in both whole cells and isolated nuclei . The effect of temperature is selective for the RNA polymerases bound to the nuclear template but not for the total RNA polymerases . Thus, the specific activities and total amounts of RNA polymerase species extracted and assayed with exogenous DNA template are similar in the ts-187 cultured at 23 degrees C and at 36 degrees C . On the contrary, the nuclear polymerases, i.e., RNA synthesis in isolated nuclei, are dramatically inhibited in cells cultured at 36 degrees C . When amino acid starved ts-187 cells are transferred to 36 degrees C, release from the inhibtion of RNA synthesis is observed . As with the addition of cycloheximide, this relaxation is observed in cells but not in isolated nuclei . The parental strain, A364A, which responds by stimulating instead of inhibiting protein synthesis when the temperature is increased to 36 degrees C, also exhibits an inhibition in the incorporation of labeled precursor into RNA as well as reducing RNA synthesis in isolated nuclei . However, these are transitory inhibitions and afterward there is reinitiation of both processes . Reinitiation of RNA synthesis in isolated nuclei is similar to the relaxed phenomenon and it is called "nuclear relaxation" . This relaxation can only be obtained if protein synthesis is not inhibited; however, cellular relaxation occurs in the absence of protein synthesis . The repression of the nuclear RNA polymerase activities which starvation and inhibition of protein synthesis produce appears to be due to a restriction in the nuclear DNA template . This notion is supported by the fact that a net diminution of these nuclear enzyme activities is observed in spheroplasts cultured under starving conditions . Studies of the four main ribonucleotide pools indicate that stringency and inhibition of protein synthesis (ts-187 cultured at 36 degrees C) produce an increase in UTP and CTP pools . This is consistent with the concept that stringency and inhibition of protein synthesis affect the rate of utilization rather than the synthesis of these ribonucleotide residues . In the A364A and ts-187 yeast strains, the conversion of uracil but not of uridine into the UTP and CTP is inhibited when there is inhibition of the nuclear RNA polymerases . This indicates that the uracil phosphoribosyltransferase but not the uridine-cytidine kinase is allosterically inhibited by UTP and CTP in yeast . The feedback inhibition in the metabolic pathway of the base explains why relaxation cannot be detected when uracil instead of uridine is used as the labeled RNA precursor.

Eur J Biochem, 1976 May 17, 65(1), 95 - 105
The cytochrome bc1 complex of yeast mitochondria . Isolation and partial characterization of the cytochrome bc1 complex and cytochrome b; Katan MB et al.; We have isolated the cytochrome bc1 complex and some of its constituent polypeptides from bakers yeast and have studied its spectroscopy, electrophoresis and amino acid analysis . The isolated complex contained 6 mumol of b heme and approximately 3 mumol of c1 heme per g of protein . The electron paramagnetic resonance spectrum was similar to that of the beef-heart preparation . The complex consisted of 7 polypeptides with mobilities on sodium dodecylsulphate polyacrylamide gel electrophoresis corresponding to Mr 44,000, 40,000, 32,000, 32,000, 17,000, 14,000 and 11,000 . One of the polypeptides with Mr 32,000 was identified on sodium dodecylsulphate gels as cytochrome c1 by porphyrin fluorescence . Cytochrome b was isolated from the complex by treating it with guanidine hydrochloride; it had a purity of 20 mumol per g of protein and consisted of a polypeptide with Mr 32,000 plus two minor bands with Mr 14,000 and 11,000 . We have isolated the polypeptide of Mr 32,000 from cytochrome b and the polypeptides of Mr 44,000 and 40,000 ("core proteins") from the complex, both by preparative sodium dodecylsulphate gel electrophoresis and determined their amino acid composition . Only the b polypeptide of Mr 32,000 shows the low proportion of polar amino acid residues that is considered typical of membrane proteins.

Eur J Biochem, 1976 May 17, 65(1), 49 - 60
The transport of S-adenosyl-L-methionine in isolated yeast vacuoles and spheroplasts; Schwencke J et al.; 1 . The properties of S-adenosyl-L-methionine accumulating system for both vacuoles and spheroplasts are described . Yeast vacuoles were obtained by a modified metabolic lysis procedure from spheroplasts of Saccharomyces cerevisiae . 2 . Isolated vacuoles accumulate S-adenosyl-L-methionine by means of a highly specific transport system as indicated by competition experiments with structural analogs of S-adenosyl-L-methionine . The S-adenosyl-L-methionine transport system shows saturation kinetics with an apparent Km of 68 muM in vacuoles and 11 muM in spheroplasts . 3 . S-Adenosyl-L-methionine accumulation into vacuoles does not require glucose, phosphoenolpyruvic acid, ATP, ADP nor any other tri- or di-phosphorylated nucleotides . It is insensitive to azide and 2,4-dinitrophenol which strongly inhibit the glucose-dependent accumulation of S-adenosyl-L-methionine in spheroplasts . 4 . The transport of S-adenosyl-L-methionine into vacuoles is optimal at pH 7.4 and is insensitive to nystatin while the uptake of S-adenosyl-L-methionine into spheroplasts is optimal at pH 5.0 and is strongly sensitive to nystatin . On this basis it has thus been possible to measure both the intracytoplasmic and the intravacuolar pool of S-adenosyl-L-methionine . 5 . Our results indicate the existence of a highly specific S-adenosyl-L-methionine transport system in the vacuolar membrane which is clearly different from the one present in the plasma membrane of yeast cells.

Eur J Biochem, 1976 May 17, 65(1), 41 - 7
Studies on the active site of yeast hexokinase . Specific phosphorylation of a serine residue induced by D-xylose and ATPMg; Menezes LC et al.; Yeast hexokinase A(ATP:D-hexose 6-phosphotransferase) is inactivated when incubated in the presence of xylose and ATPMg, or in the presence of D-lyxose in a reaction medium in which ATPMg is being continuously regenerated (phosphoenolpyruvate and pyruvate kinase) . The inactivation is due to the phorphorylation of the protein . A linear relationship was observed between the inactivation and the incorporation of 32P from {gamma-32P} ATP . All hexokinase and ATPase activity of the enzyme is lost when one phosphoryl group is incorporated per enzyme subunit (molecular weight 51,000) . The phosphoryl group is covalently bound by a ester linkage with a serine residue of the protein.

Biochim Biophys Acta, 1976 May 13, 429(3), 933 - 49
Yeast aminopeptidase I . Chemical composition and catalytic properties; Metz G et al.; An aminopeptidase (alpha-aminoacyl L-peptide hydrolase, EC 3.4.11.1) was purified to homogeneity from autolysates of brewer's yeast . The enzyme which is responsible for most of the yeast cell's aminopeptidase activity is a glycoprotein containing about 12% of conjugated carbohydrate and 0.02% Zn2+ and having a complex quaternary structure . The active species has a molecular weight of approx . 600000 and an isoelectric point of 4.7 . The enzyme is remarkably stable, even in dilute solutions . All types of L-amino acid and peptide derivatives containing a free amino terminus are attacked, including amino acid amides and esters . As to its substrate specificity, the enzyme belongs to the so called leucine-aminopeptidases . It is strongly and specifically activated by Zn2+ and Cl- (or Br-) and inactivated by metal-chelating agents . The activation by Zn2+ seems to be mediated by a conformational transition which affects exclusively V and leads to a form of the enzyme which enhanced stability against heat . Halide anions, on the other hand, are acting as positive allosteric effectors, modulating both V and Km.

J Biol Chem, 1976 May 10, 251(9), 2611 - 2
Cr(III) complexes as active site probes of yeast inorganic pyrophosphatase; Sperow JW et al.; The inert coordination complex of Cr(III) with PP1 (CrPP1) is not a substrate for yeast inorganic pyrophosphatase and does not inhibit the Mg2+-dependent activity of this enzyme . These results, when compared with the effects of CrPP1 on other enzymes and with the effects of other divalent metal ions on this enzyme, suggest that yeast inorganic pyrophosphatase binds substraather than the phosphate groups . Mg2+ partially protects against a slow inactivation of the enzyme by Cr(H2O)6(3)+; this exchange inert ion may provide a means of labeling the metal ion binding site of this enzyme.

Nature, 1976 May 6, 261(5555), 26 - 9
Production of yeast alcohol dehydrogenase isoenzymes by selection; Wills C; Mutants of yeast alcohol dehydrogenase have been produced that protect the cell against the poisonous aldehyde acrolein by increasing the NADH-NAD ratio . The altered properties include changes both in binding constants and in cooperativity . Such mutants may be useful in exploring the nature of adaptation at the molecular level.

Biochemistry, 1976 May 4, 15(9), 2018 - 26
Isotope effects and structure-reactivity correlations in the yeast alcohol dehydrogenase reaction . A study of the enzyme-catalyzed oxidation of aromatic alcohols; Klinman JP; Steady-state kinetic parameters for the yeast alcohol dehydrogenase catalyzed oxidation of a series of parasubstituted benzyl alcohols-1, 1-h2 and -1, 1-d2 by NAD+ are reported . Catalytic constants have been found to be characterized by large deuterium isotope effects: kH/kD=4.8, p-Br; 4.2, p-Cl; 3, 4, p-H; 4, 2, p-CH3; 3, 2, p-CH3O . The observed isotope effects on k(cat)/K(A), K(A), and K(B), where K(A) and K(B) are Michaelis constants for NAD+ and alcohol, indicate a borderline rapid equilibrium-steady-state kinetic mechanism involving the random addition of substrate and coenzyme to enzyme . With the exception of p-CH3 and possible p-CH3O substituted benzyl alcohol, k(cat) is concluded to represent a single, rate-limiting hydrogen transfer step . A multiple linear regression analysis of the combined data for benzaldehyde reduction (Klinman, J.P . (1972), J . Biol . Chem . 247, 7977-7987, expanded to include p-CH(CH3) 2-substituted benzaldehyde) and benzyl alcohol oxidation has been carried out to determine the contribution of electronic, hydrophobic, and steric effects to k(cat) and substrate binding . Benzaldehyde binding is concluded to depend on electronic substituent effects as previously reported {log 1/K(ald)=(-0.92 +/- 0.18)sigma+-(0.80 +/- 0.067)}, whereas benzyl alcohol binding correlates with substrate hydrophobicity {(log 1/K(alc)=(0.60 +/- 0.14) log P -(1.2 +/- 0.12)} . In the case of benzyl alcohol oxidation, k(cat) is independent of electronic and steric effects; the best of seven equations indicates a small negative dependence of k(cat) on hydrophobicity, which is within experimental error or zero {log k(o)=(-0.075 +/- 0.25) log P -(0.65 +/- 0.19)} . Data for benzaldehyde reduction are correlated at the 99% significance level by a single variable equation {(log k(R)=(2.1 +/- 0.37) sigma+-(0.093 +/- 0.14)} and a two variable equation {(log k(R)=(1.9 +/- 0.33) sigma+ + (0.46 +/- 0.20) log P-(0.46 +/- 0.20)}; these equations indicate (a) a large dependence on electronic substituent as reported previously and (b) a possible role for hydrophobic factors in facilitating catalysis . As the result of the observed hydrophobic substituent effects, different ground-state interactions are suggested for the binding of benzaldehydes and benzyl alcohols . Electronic substituent effects lead to the conclusion that there is little or no change in charge at C-1 of substrate at the transition state, relative to alcohol in the ground state . The significance of these effects to the detailed properties of the hydrogen transfer step is discussed.

Biochemistry, 1976 May 4, 15(9), 1883 - 8
A study of secondary and tertiary solution structure of yeast tRNA(Asp) by nuclear magnetic resonance . Assignment of G.U ring NH and hydrogen-bonded base pair proton resonances; Robillard GT et al.; The 270-MHz spectra of yeast tRNA(Asp) in H2O solutions containing Mg2+ show clearly resolved resonances in the region from -15 to -9.5 ppm . Resonances between -15 and -11.5 ppm from the hydrogen-bonded protons of the acceptor stem and anticodon arm decrease in intensity with increasing temperature and disappear by 75 degrees C . Simultansously, four well-resolved resonances between -11.2 and -10.3 ppm also decrease in intensity and disappear . Because of this behavior and their positions these resonances have been assigned to the four ring NH protons of G.U base pairs 5 and 30 in the acceptor stem and anticodon arm which are thereby shown not to be hydrogen bonded by normal Watson-Crick hydrogen bonds . The five G.C base pair resonances of the T psi C arm remain visible above 70 degrees C after all other resonances have disappeared . The high-temperature tRNA spectrum agrees well with that of the isolated T psi C hairpin and CCA half-molecule fragments, each of which contains the same five hydrogen-bonded proton resonances . The root-mean-square error between the observed and calculated resonance positions for the hydrogen-bonded base pair protons of these three arms is 0.19 ppm . The dihydrouridine stem is expected to have two A.U Watson-Crick base pairs and no B.C base pairs . However, it does not contribute any hydrogen-bonded resonances to the nuclear magnetic resonance (NMR) spectrum below -11.5 ppm . This suggests that even at 35 degrees C this helix is not hydrogen bonded in a normal manner . In the region below -11.4 ppm there are three additional proton resonances melting earlier than the rest which cannot be assigned to a particular helix of the cloverleaf . We suggest that these resonances arise from hydrogen-bonded protons involved in stabilizing tertiary structure.

Biochemistry, 1976 May 4, 15(9), 1874 - 82
Thermal unfolding of yeast glycine transfer RNA; Hilbers CW et al.; In the present investigations the molecular unfolding of yeast tRNA(Gly) has been studied by a combination of nuclear magnetic resonance spectroscopy, melting techniques, and relaxation kinetics . From these studies the following pathway of unfolding was found . In a coupled melting transition the tertiary, the DHU, and the anticodon structure are disrupted . This is followed by the melting of the acceptor arm, while the T psi C arm, which only contains G-C pairs, melts out last . Interestingly, during the first melting transition a new structure not belonging to the original cloverleaf structure is formed . The thermodynamic and kinetic parameters of the melting transitions were determined and are discussed in relation to earlier work . The present nuclear magnetic resonance (NMR) experiments as well as earlier studies show that the ring current calculations based on the cloverleaf structure provide a good first-order interpretation of the NMR spectra of tRNA.

Biochemistry, 1976 May 4, 15(9), 1975 - 87
Glucose-6-phosphate dehydrogenase from brewers' yeast . The effects of pH and temperature on the steady-state kinetic parameters of the two-chain protein species; Kuby SA et al.; A systematic study has been made of the pH- and temperature-dependency of the steady-state kinetic parameters of the stabilized two-subunit enzyme species of glucose-6-phosphate dehydrogenase, in the absence of superimposed association-dissociation reactions . The Vmax(app) data obtained in several buffers between pH 5 and 10 and at 18-32 degrees C lead to the postulate that at least two sets of protonic equilibria may govern the catalysis (one near pH 5.7 AT 25 DEGREES C and another near pH 9.2); furthermore, two pathways for product formation (i.e., two Vmax's) appear to be required to explain the biphasic nature of the log Vmax(app) vs . pH curves, with Vmax(basic) greater than Vmax(acidic + neutral) . Of the several buffers explored, either a uniform degree of interaction or a minimal degree of buffer species interaction could be assessed from the enthalpy changes associated with the derived values for ionization constants attributed to the protonic equilibria in the enzyme-substrates ternary complexes for the case of Tris-acetate-EDTA buffers, at constant ionic strength . With the selection of this buffer at 0.1 (T/2) and at 25 and 32 degrees C, a self-consistent kinetic mechanism has emerged which allows for the random binding of the two fully ionized substrates to the enzyme via two major pathways, and product formation by both E-A--B- and HE-A--B- . As before (Kuby et al . Arch . Biochem, Biophys . 165, 153-178, 1974), a quasi-equilibrium is presumed, with rate-limiting steps (k + 5 and k + 5') at the interconversion of the ternary complexes . Values for the two sets of protonic equilibria defined by this mechanism (viz., pKk, pKH2 for the first ionizations, and pKk', pKH' for the second) could then be estimated . From their numerical values (e.g., at 25 degrees C: pKK = 5.7 PKH2 = 5.2; and pKK' = 9.1, PKH' = 8.2) and from the values for delta H degrees ioniz (e.g., delta H degrees pKK APPROXIMATELY 5.1 KCAL/MOL; DELTA H degrees pKK' APPROXIMATELY 11 KCAL/MOL), A POSTULATE IS PRESENTED WHICH ATTRIBUTES THESE Acid dissociation constants to an imidazole and epsilon-amino group, respectively.

Arch Microbiol, 1976 May 3, 108(1), 141 - 3
Sporobolomyces salmonicolor var . fischerii, a new yeast; Misra VC et al.; A new variety of Sporobolomyces salmonicolor, a basidiomycetous yeast isolated from the cerebrospinal fluid of a human case of meningitis has been described . The variety can be differentiated from the species primarily by its ability to assimilate D-galactose and L-arabinose.

J Bacteriol, 1976 May, 126(2), 959 - 68
Respiratory-deficient mutants of Torulopsis glabrata, a yeast with circular mitochondrial deoxyribonucleic acid of 6 mu m; O'Connor RM et al.; Purified mitochondria from the petite positive yeast Torulopsis glabrata contain a circular deoxyribonucleic acid (DNA) with a length of 6 mum and a buoyant density of 1.686 g/cm3 . This DNA is absent from ethidium bromide induced respiratory-deficient mutants.

Nucleic Acids Res, 1976 May, 3(5), 1151 - 65
Nuclear origin of specific yeast mitochondrial aminoacyl-tRNA synthetases; Schneller JM et al.; Hydroxylapatite chromatographies of mitochondrial and total enzymes from a rho+ yeast, or from the related rho degrees mitochondrial DNA-less mutant, show the occurrence in the mitochondrial enzyme of one Phe-, one Met-, one Leu-tRNA synthetase peak which elutes distinctly from the cytoplasmic counterpart and charges well mitochondrial tRNA, whereas the cytoplasmic enzyme does not . The measurement of the mitochondrial synthetases activities in various enzymatic extracts shows that they are not repressed in rho+ cells grown on 10% glucose and that they are concentrated in the mitochondria (Phe- and Met- tRNA synthetases) but are also present outside the mitochondria . It is concluded that yeast mitochondrial protein biosynthesis involves the nuclear coded mitochondrial specific Phe-, Met- and Leu-tRNA synthetases and that the entrance of the synthetases into the mitochondria needs no factor depending on the mitochondrial DNA.

Eur J Biochem, 1976 May 1, 64(2), 507 - 10
Thermal melting curves of tRNAPhe from yeast lacking different numbers of nucleotides from the 3'-end; Beltchev B et al.; The thermal melting curves of tRNAPhe and tRNALys from yeast lacking different numbers of nucleotides from the 3'-end were recorded . The removal of the first nucleotide had no effect on the melting profile . The stepwise removal of the following six nucleotides caused changes in the character of the derivative melting curves: they became rather broad and melting started at lower temperatures . These results indicate that the nucleotides at the 3'-end contribute to the stability of the molecular structure of tRNAs.

J Bacteriol, 1976 May, 126(2), 1012 - 3
Enzymatic analysis of C27 sterol-accumulating yeast strains; Bailey RB et al.; Several strain of bakers' yeast that accumulate only C27 sterols were analyzed for sterol methyltransferase activity, with no activity being found . Cholesta-5,7,22,24-tetraene-3beta-ol, one of the mutants' sterol products, was found to be an unacceptable substrate for in vitro transmethylation.

Hoppe Seylers Z Physiol Chem, 1976 May, 357(5), 735 - 40
Inactivation of yeast enzymes by proteinase A and B and carboxypeptidase Y from yeast; Jusic M et al.; Changes in the activities of 15 different enzymes during incubation of a crude yeast extract with the purified yeast proteinases A and B, and carboxypeptidase Y, respectively, have been measured . The spectrum of action of the three proteinases on the enzymes measured differs significantly, increasing or decreasing their activities or having no effect . Incubation of purified cytoplasmic malate dehydrogenase or purified mitochondrial malate dehydrogenase with proteinases A and B results in selective inactivation of the cytoplasmic enzyme, whereas the mitochondrial activity is not affected . Carboxypeptidase Y has no effect on the activity of either dehydrogenase . The results support the idea of selective proteolysis as the mechanism of the earlier observed inactivation of cytoplasmic malate dehydrogenase, initiated by the addition of glucose to intact yeast cells grown on acetate as carbon source ("glucose effect").

Hoppe Seylers Z Physiol Chem, 1976 May, 357(5), 727 - 34
Studies on the proteinase-A inhibitor I3A from yeast; Nunez de Castro I et al.; The purification and some properties of the two inhibitors I2A and I3A of proteinase A from yeast have previously been described {Saheki et al, (1974) Eur . J . Biochem . 47, 325} . An improved method for the preparation of I3A which is less time-consuming and leads to higher yields is presented . Based on amino acid analysis, I3A contains 68 amino acids per molecule . The molecular weight was 7676 . The inhibitor contained no proline, no arginine, no cysteine and no tryptophan, but did contain a large number of the polar amino acids glutamate + glutamine, aspartate + asparagine and lysine . Neither by dansylation nor by Edman degradation could an N-terminal amino acid be detected . Changes in the circular dichroism upon transition from pH 6.9 to 3.0 suggest different tertiary structures at these pH values . Experiments on the kinetics of inhibition of proteinase A revealed an apparent Ki value of 5.5 X 10(-8) M for I3A and 1.6 X 10(-8) M for pepstatin . A "non-stoichiometric inhibition" of a "pseudo-irreversible" type is concluded from the kinetic data . A hydrophobic type of binding of I3A to yeast proteinase A is suggested from experiments demonstrating a large decrease in the percentage of inhibition caused by addition of 2 M urea, 2 M guanidine hydrochloride, 0.125% Triton or 0.125% cholic acid.

Can J Biochem, 1976 May, 54(5), 432 - 7
Kinetic effect of some aliphatic amines on yeast alcohol dehydrogenase; Dove MJ et al.; Initial rate studies of ethanol oxidation catalyzed by yeast alcohol dehydrogenase (EC 1.1.1.1) were carried out in the presence of varying concentrations of aliphatic amines over the pH range from 8.0 to 10.5 . Aliphatic amines either activate or inhibit the enzyme depending on whether the pH is greater or less than 9.5 suggesting that the protonated amines activate and the nonprotonated amines inhibit the enzyme . Aliphatic amines activate yeast alcohol dehydrogenase by decreasing Kb while they inhibit the enzyme by increasing both Ka and Kia . When both protonated and nonprotonated amines are present in solution, either overall activation or inhibition will be observed depending on the relative concentration of the two amine species.

J Bacteriol, 1976 May, 126(2), 919 - 27
Development of Microbodies in the yeast Kloeckera growing on methanol; Tanaka A et al.; A number of microbodies appear regularly in methanol-grown yeast cells, but rarely in ethanol- or glucose-grown cells . When one of representative methanol-utilizing yeasts, Kloeckera sp.no . 2201 (also known as Candida bodinii), was cultured on glucose and then transferred into a methanol medium, microbodies of small size could be observed in 2-h old cells . The number of microbodies per sectioned cell reached five to six after 4 h of cultivation . Though the number of microbodies did not change during prolonged cultivation, their size became larger with the passage of cultivation time . The activities of catalase and alcohol oxidase were confirmed in the particulate fractions throughout the cultivation period, whereas the activities of formaldehyde dehydrogenase and formate dehydrogenase were not detected in the particles . The activity of isocitrate lyase was detected in the particulate fractions only at the early growth phase.

Mol Gen Genet, 1976 Apr 23, 145(1), 43 - 52
Biogenesis of mitochondria 44 . comparative studies and mapping of mitochondrial oligomycin resistance mutations in yeast based on gene recombination and petite deletion analysis; Trembath MK et al.; A comparative study of eight independently isolated mitochondrial oligomycin resistant mutants obtained from three laboratories show a variety of phenotypes based on cross resistance to venturicidin and sensitivity to low temperature . Analysis of recombination between pairs of markers indicate the existence of at least three genetic classes; class A, cross resistant to venturicidin and including the mutations OIII, {olil-r}, {olgi-R}, {tso-r}; class B, mutations OI, {olil7-r}, {OLG2-R}; and class C, the mutation O11 . The recombination data is consistent with mutations of each class residing in three separate genes, although mutations of class A and B show very close linkage . Recombination in non-polar crosses had demonstrated that markers of all three classes are linked to the mikl locus in the configuration (AB)-mikl-C . The mapping of this segment with respect to other markers of the mitochondrial genome and the order of classes A and B was established by analysis of co-retention frequenceis of markers in primary petite isolates as well as by analysis of marker overlap of genetically and physically defined petite genomes . The unambiguous order eryl-A-B-mik1-C-par was obtained . DNA-DNA hybridization studies using mtDNA isolated from selected petites confirms this map and estimates the physical separation of markers . A resonable correlation exists in this region of th genome between distances estimated physically by hybridization and genetically by frequencey of recombination in non-polar crosses . It is potulated that the oligomycin-mikamycin linkage group represents a cluster of genes involved in determing a number of mitochondrial membrane proteins associated with the mitochondrial ATPase and respiratory complex III.

Mol Gen Genet, 1976 Apr 23, 145(1), 37 - 42
Haemoprotein formation in yeast . II . Isolation of catalase regulatory mutants; Rytka J et al.; A procedure was described for the isolation of mutants affected in the regulation of catalase activity . Two such mutants, cgr 1 and cgr 2 were obtained . Both of them show catalase activity that is resistant to repression by glucose, but is sensitive to anoxia to the same extent as the wild type.

Mol Gen Genet, 1976 Apr 23, 145(1), 73 - 9
Study on proteins from yeast cytoplasmic ribosomes by two-dimensional gel electrophoresis; Ishiguro J; Proteins of yeast cytoplasmic ribosomes were analyzed by two different methods of two dimensional gel electrophoresis: run at pH 8.6 in 1-D1 and at pH 4.6 in 2-D (Method A); run at pH 5.0 in 1-D and in the presence of sodium dodecyl sulfate in 2-D (Method B) . The numbers of proteins estimated were 28 (Method A) and 29 or 30 (Method B) in the 40S small subunit, and 40 (Method A) and 41 (Method B) in the 60S large subunit, respectively . Molecular weights of proteins in the small and the large subunits were found to be less than 40,000 and 60,000 respectively.

Biochim Biophys Acta, 1976 Apr 15, 432(1), 92 - 7
Distribution of membrane-bound and free ribosomes in growing yeast; Schneider E et al.; 1 . The distribution of membrane-bound and free ribosomes was investigated in stationary as well as in growing yeast cells . the relative amount of free ribosomes varies with the growth phase of the cell culture . During the duplication phases of the cell, relative maxima of free ribosomes can be found . However, the absolute amount of free ribosomes is fairly constant during the growth of the cells . 2 . Membrane-bound ribosomes show lower polypeptide synthesis activity in a cell-free, poly (U)-dependent system than free ribosomes . 3 . There is no difference in the distribution pattern of free and membrane-bound ribosomes in growing yeast cells of different ploidy . 4 . A turnover between free and membrane-bound ribosomes is suggested to be in agreement with the hypothesis of Branes and Pogo ((1975) Eur . J . Biochem . 54, 317-328).

J Biol Chem, 1976 Apr 10, 251(7), 1997 - 2004
Cytochrome c1 of bakers' yeast . II . Synthesis on cytoplasmic robosomes and influence of oxygen and heme on accumulation of the apoprotein; Ross E et al.; In the preceding paper (Ross, E., and Schatz, G . (1976) J . Biol . Chem . 251, 1991-1996) yeast cytochrome c1 was characterized as a 31,000 dalton polypeptide with a covalently bound heme group . In order to determine the site of translation of this heme-carrying polypeptide, yeast cells were labeled with {H}leu(be under the following conditions: (a) in the absence of inhibitors, (b) in the presence of acriflavin (an inhibitor of mitochondrial translation), or (c) in the presence of cycloheximide (an inhibitor of cytoplasmic translation) . The incorporation of radioactivity into the hemeprotein was measured by immunoprecipitating it from mitochondrial extracts and analyzing it by dodecyl sulfate-polyacrylamide gel electrophoresis . Label was incorporated into the cytochrome c1 apoprotein only in the presence of acriflavin or in the absence of inhibitor, but not in the presence of cycloheximide . Cytochrome c1 is thus a cytoplasmic translation product . This conclusion was further supported by the demonstration that a cytolasmic petite mutant lacking mitochondrial protein synthesis still contained holocytochrome c1 that was indistinguishable from cytochrome c1 of wild type yeast with respect to molecular weight, absorption spectru, the presence of a covalently bound heme group, and antigenic properties . Cytochrome c1 in the mitochondria of the cytoplasmic petite mutant is firmly bound to the membrane, and its concentration approaches that typical of wild type mitochondria . However, its lability to proteolysis appeared to be increased . A mitochondrial translation product may thus be necessary for the correct conformation or orientation of cytochrome c1 in the mitochondrial inner membrane . Accumulation of cytochrome c1 protein in mitochondria is dependent on the abailability of heme . This was shown with a delta-aminolevulinic acid synthetase-deficient yeast mutant which lacks heme and any light-absorbing peaks attributable to cytochromes . Mitochondria from mutant cells grown without added delta-aminolevulinic acid contained at least 20 times less protein immunoprecipitable by cytochrome c1-antisera than mitochondria from cells grown in the presence of the heme precursor . Similarly, the respiration-deficient promitochondria of anaerobically grown wild type cells are almost completely devoid of material cross-reacting with cytochrome c1-antisera . A 105,000 X g supernatant of aerobically grown wild type cells contains a 29,000 dalton polypeptide that is precipitated by cytochrome c1-antiserum but not by nonimmune serum . This polypeptide is also present in high speed supernatants from the heme-deficient mutant or from anaerobically gorwn wild type cells . The possible identity of this polypeptide with soluble apocytochrome c1 is being investigated.

J Biol Chem, 1976 Apr 10, 251(7), 1991 - 6
Cytochrome c1 of bakers' yeast . I . Isolation and properties; Ross E et al.; Cytochrome c1 has been purified from mitochondria of the yeast Saccharomyces cerevisiae . The procedure involves solubilization withcholate, ammonium sulfate fractionation, disruption of the dytochrome b-c1 complex with mercaptoethanol and detergents, and chromatography on DEAE-cellulose . The final product is psectrally pure, contains up to 62 nmol of covalently bound heme per mg of protein and does not react with oxygen or carbon monoxide . Sodium dodecyl sulfate disaggregates the purified cytochrome into a single 31,000 dalton subunit carrying the covalently attached heme group . Many cytochrome c1 preparations contain in addition an 18,500 dalton polypeptide which is devoid of covalently bound heme . Since this polypeptide can be removed from the heme-carrying polypeptide by relatively mild procedures, it is probably not an essential subunit of cytochrome c1 . Cytochrome c1 is extremely sensitive to proteolysis . If it si purified in the absence of protease inhibitors, a family of heme polypeptides with molecular weights of 29,000, 27,000, and 25,000 daltons is obtained . In the presence of the protease inhibitor phenylmethylsulfonylfluoride the purification yields predominantly a 31,000 dalton heme protein with only little contamination by a 29,000 dalton degradation product . In order to show that only the 31,000 dalton heme-polypeptide is the native species, yeast cells were labeled with the heme-precursor delta-amino{3H}levulinic acid, converted to protoplasts and directly lysed with dodecyl sulfate in the presence of protease inhibitors . Subsequent electrophoresis of the lysate in the presence of dodecyl sulfate reveals the covalently bound heme of cytochrome c1 as a single symmetrical peak at 31,000 daltons.

Biochim Biophys Acta, 1976 Apr 8, 429(2), 324 - 30
Purification and properties of NADP-dependent glutamate dehydrogenase from yeast nuclear fractions; Camardella L et al.; 1 . NADP-dependent glutamate dehydrogenase (EC 1.4.1.4) extracted from nuclear fractions of Saccharomyces cerevisiae was partially purified . The final purification achieved was over 100-fold over the initial extract . 2 . Cellulose acetate electrophoresis shows that the preparation is close to homogeneity and that the enzyme is slightly more anionic than cytoplasmic glutamate dehydrogenase . 3 . The response of the nuclear activity to variation of pH, of inorganic phosphate and other electrolyte concentration and of the concentration of the reaction substrates has been investigated . Several differences were detected in comparison with cytoplasmic glutamate dehydrogenase.

Biochim Biophys Acta, 1976 Apr 5, 426(4), 745 - 56
Kinetics of ion translocation across charged membranes mediated by a two-site transport mechanism . Effects of polyvalent cations upon rubidium uptake into yeast cells; Theuvenet AP et al.; (1) The effect of surface charge upon the kinetics of monovalent cation translocation via a two-site mechanism is investigated theroretically . (2) According to the model dealt with, typical relations are expected for the dependence of the kinetic parameters of the translocation process upon the concentration of a polyvalent cation, differing essentially from those derived for the case in which the membrane carries no excess charge . (3) Even when a polyvalent cation does not compete with the substrate cation for binding to the translocation sites, apparently competitive inhibition may occur when the membrane is negatively charged . (4) The model is tested experimentally by studying the effects of the polyvalent cations Mg2+, Sr2+, Ca2+, Ba2+ and Al3+ upon Rb+ uptake into yeast cells at pH 4.5 A good applicability is found . (5) Equimolar concentrations of polyvalent cations reduce the rate of the Rb+ uptake into yeast cells in the order Mg2+ less than Sr2+ less than Ca2+ less than Ba2+ less than Al3+ . (6) The conclusion is reached that the reduction in the rate of Rb+ uptake caused by the polyvalent cations applied results mainly from screening of the negative fixed charges on the membrane surface and binding to these negative sites rather than competition with Rb+ for the transport sites . (7) The results of our investigation indicate the affinity of the alkaline-earth cations for the negative fixed charges on the surface to the yeast cell membrane increases in the orther Mg2+ less than Sr2 less than Ca2+ less than Ba2+ . (8) Probably mainly phosphoryl groups determine the net charge on the membrane of the yeast cell at a medium pH of 4.5.

Biochim Biophys Acta, 1976 Apr 2, 425(4), 401 - 8
Methylated nucleosides in polyadenylate-containing yeast messenger ribonucleic acid; De Kloet SR et al.; Yeast messenger RNA was found to be methylated . A calculation of the specific methylation showed that the average yeast messenger RNA molecule contains only two methylated nucleosides which occur in one alkali stable oligonucleotide . Similar to other eukaryotic messengers, the 5' terminus of yeast messenger RNA is blocked by 7-methylguanosine, linked through a di- or triphosphate bridge to a ribosemethylated nucleoside . Contrary to the messengers of high eucaryotic organisms, no additional base methylated constituents were found.

Mol Biol Rep, 1976 Apr, 2(5), 393 - 400
Topographical analysis of yeast ribosomal DNA by cleavage with restriction endonucleases; Meyerink JH et al.; Yeast ribosomal DNA (rDNA) was digested with the restriction enzymes Hind III, Hind II and a mixture of Hind II and Hind III . The cleavage products were analyzed by electrophoresis on 1.5% agarose gels . Several distinct bands could be observed, which are derived from the redundant ribosomal transcription units . They are superimposed on a rather broad smear of background DNA, representing the heterogenous 'spacer' sequences . From the restriction maps, together with data obtained by partial digestion, a physical map for the ribosomal transcription unit in yeast could be constructed.

Arch Tierernahr, 1976 Apr, 26(4), 267 - 74
{Protein utilization of mixed feed rations in lactating pigs with reference to the essential amino acid content of the feed proteins . 2 . Report . Utilization of the feed proteins in the use of soy bean extraction residue, waste liquor yeast, horse bean meal fish meal and maize gluten for a basic ration}; Kracht W et al.; Nitrogen trials were performed on lactating pigs to investigate the utilization of protein from some feeding rations . The basal ration fed to the sows consisted of ground barley+oats+flaked potatoes or ground barley+sugar beet chips . The basal ration was supplemented with a protein source . The protein feeds used were extracted soya bean meal, horse bean meal, fish meal, maize gluten and waste liquor yeast . Data for the average biological value of the dietary proteins were as follows (in the given order of protein feeds): 61%, 59%, 54%, 58% and 37% . PPV data were: 44%, 43%, 39%, 44% and 28% . The proteins of nearly all rations were deficient in lysine when compared with the range of amino acids present in the proteins of sow milk.

Ann Microbiol (Paris), 1976 Apr, 127(3), 353 - 66
{Lysine and arginine requirement of "Ustilago cynodontis" 4001 yeast-like cells . I . --Growth in the presence and in the absence of lysine (author's transl)}; Delavier-Klutchko C et al.; For optimal growth, the yeast-like cells of Ustilago cynodontis 4001 (originating from the mycelium 4001 prototroph forms) require the presence of both arginine and lysine . However, in the absence of lysine, growth does occur, but two exponential growth phases can then be observed: a pseudo-lag phase during which the growth rate is slow, and a second, true exponential phase . The initial OD of the culture and the arginine concentration of the medium do not appear to affect the duration of the pseudo-lag phase . The arginine concentration does, however, affect the growth yield . Upon addition of lysine to the culture medium, the period of the pseudo-lag phase is reduced and the growth rate increased . The pseudo-lag phase can be completely suppressed by the addition of adequate amounts of lysine . In the presence of lysine and in the absence of arginine, cells are not capable of multiplication . Addition of arginine initiates growth; whether or not a lag phase occurs depends on the quantity of arginine added . The successive inoculation of cells into lysine-free medium leads to suppression of the pseudo-lag phase but only after three or four passages . Therefore it does not seem that there is selection of cells which do not require lysine during the pseudo-lag phase . It is shown that it is not the modification of the culture medium which suppresses the lysine requirement: the cells which are put to grow in the supernatant of a culture in which a pseudo-lag phase had taken place behave in the same way that when they are inoculated in a new medium . The modification of the cell metabolism itself is discussed.

Hoppe Seylers Z Physiol Chem, 1976 Apr, 357(4), 509 - 26
{Isolation and characterization of seryl- and phenylalanyl-tRNA synthetase from yeast (author's transl)}; Hirsch R et al.; A procedure for the simultaneous isolation of seryl- and phenylalanyl-tRNA synthetase from yeast is described . In addition some other synthetases as well as tRNA nucleotidyltransferase can be obtained in an enriched state . The isolated seryl- and phenylalanyl-tRNA synthetases were compared to earlier preparations with respect to purity, specific activity, and structure . Previous investigations with fluorescence spectroscopy and kinetic methods were complemented and extended by experiments on the specificity of aminoacylation and on the isolation, by sucrose gradient centrifugation, of complexes between synthetase and tRNA or tRNA fragments . A protection of synthetases against inactivation by addition of substrates was observed . The dissociation of seryl-tRNA synthetase, at low concentrations, into monomer subunits was investigated by chemical modification with bifunctional reagents and by kinetic experiments . By modification of SH-groups fluorescent dyes were incorporated into both, seryl- and phenylalanyl-tRNA synthetase which retained most of their activity . The binding of tRNAPhe to phenylalanyl-tRNA synthetase which had been modified with pyrene maleimid was followed by fluorescence intensity measurements.

Nucleic Acids Res, 1976 Apr, 3(4), 1111 - 23
Atomic coordinates and molecular conformation of yeast phenylalanyl tRNA . An independent investigation; Stout CD et al.; The atomic coordinates of yeast tRNA(Phe) in the monoclinic crystal form have been determined by an independent analysis from a model built into a 3 A MIR map . The overall molecular structure is found to be in agreement with those reported for the same crystal form by Ladner et al . (1975) and for the orthorhombic form by Quigley et al . (1975) and Kim et al . (1975) . However, significant differences between any two of the four models are found in certain local regions of the molecule . The structure is analyzed in terms of the nucleotide stereochemistry and internucleotide phosphodiesters . A striking observation is that the majority of the nucleotide moieties occur in the conformation preferred by the constituent mononucleotides themselves . The internucleotide P-O bonds afford the primary source of flexibility for the folding of the polynucleotide backbone while the sugar pucker and C(4')-C(5') torsions provide the secondary source of flexibility.

Mutat Res, 1976 Apr, 35(1), 39 - 52
Yeast mutants resistant to basic fuchsin: a genetic approach to the integration of nuclear and mitochondrial information; Barrere G et al.; In yeast, basic fuchsin both inhibits mitochondrial functions and is a potent mutagen for the mitochondrial genome . A genetic analysis of two mutants resistant to the dye indicate that: (1) resistance is specified by a nuclear gene; (2) the onset of resistance in sensitive cells is controlled by the mitochondrial genome; and (3) sensitive mitochondrial structures can be carried over for many cell generations in the presence of a resistant nuclear genotype.

Mutat Res, 1976 Apr, 35(1), 29 - 38
Genetic effects of formaldehyde in yeast . II . Influence of ploidly and of mutations affecting radiosensitivity on its lethal effect; Chanet R et al.; Haploid and diploid cells of Saccharomyces cerevisiae have the same sensitivity to formaldehyde, exponentially growing cells being more sensitive than stationary phase cells for both degrees of ploidy . Strains defective (rad 1-3) or with a reduced capacity (p-, cytoplasmic respiratory deficient mutants) in excision repair of ultraviolet-induced pyrimidine dimers show a greater sensitivity to formaldehyde than the corresponding wild type . A mutant defective in radiation-induced gene conversion (rec5) shows the same sensitivity as the wild-type strain . It appears that the excision-repair system plays an important role, especially in stationary phase cells, in repairing a fraction of formaldehyde-induced lesions.

Biotechnol Bioeng, 1976 Apr, 18(4), 545 - 80
The kinetics of protein salting-out: precipitation of yeast enzymes by ammonium sulfate; Foster PR et al.; Protein solubility can be adequately represented by the classical Cohn equation for the salting-out of alcohol dehydrogenase and fumarase from clarified yeast homogenate with ammonium sulfate . However, the constant beta in this equation is a function of the contacting procedure employed . The kinetics of continuous salting-out were similar for alcohol dehydrogenase and fumarase . The overall rate equation for precipitation had a variable order which was high initially, up to 3.1, but approached unity on completion of precipitation . This was followed by a partial resolution stage which was first order with respect to the concentration driving force . Precipitate particle size was estimated as 0.5 to 5 mum with continuous flow precipitation producing the largest particles.

Proc Natl Acad Sci U S A, 1976 Apr, 73(4), 1083 - 6
Variant forms of mitochondrial translation products in yeast: evidence for location of determinants on mitochondrial DNA; Douglas MG et al.; Products of mitochondrial protein synthesis in yeast have been labeled in vivo with 35SO42- . More than 20 polypeptide species fulfilling the criteria of mitochondrial translation products have been detected by analysis on sodium dodecyl sulfate-exponential polyacrylamide slab gels . A comparison of mitochondrial translation products in two wild-type strains has revealed variant forms of some polypeptide species which show genetic behavior consistent with the location of their structural genes on mtDNA . Our results demonstrate the feasibility of performing genetic analysis on putative gene products of mtDNA in wild-type yeast by direct examination of the segregation and recombination behavior of specific polypeptide species.

Proc Natl Acad Sci U S A, 1976 Apr, 73(4), 1029 - 33
Transcription in yeast: alpha-amanitin sensitivity and other properties which distinguish between RNA polymerases I and III; Schultz LD et al.; Three peaks of DNA-dependent RNA polymerase (RNA nucleotidyltransferase) activity are resolved by chromatography of a sonicated yeast cell extract on DEAE-Sephadex . The enzymes, which are named RNA polymerases I, II, and III in order of elution, show similar catalytic properties to the vertebrate class I, class II, and class III RNA polymerases, respectively . Yeast RNA polymerase III is readily distinguished from yeast polymerase I by its biphasic amnonium sulfate activation profile with native DNA templates, greater enzymatic activity with poly{d(I-C)} than with native salmon sperm DNA, and distinctive chromatographic elution positions from DEAE-cellulose (0.12 M ammonium sulfate) compared with DEAE-Sephadex (0.32 M ammonium sulfate) . The three yeast RNA polymerases also show significant differences in alpha-amanitin inhibition . RNA polymerase II is the most sensitive (50% inhibition at 1.0 mug of alpha-amanitin per ml) . Contrary to the results for vertebrate systems, yeast polymerase I can be completely inhibited by alpha-amanitin at high concentrations (50% inhibition at 600 mug/ml) while yeast RNA polymerase II BEGINS TO SHOW SIGNIFICANT INHIBITION ONLY AT CONCENTRATIONS EXCEEDING 1 MG/ML . Therefore, yeast RNA polymerases I and III show a pattern of alpha-amanitin sensitivity that is the reverse of that seen for the analogous vertebrate RNA polymerases.

Proc Natl Acad Sci U S A, 1976 Apr, 73(4), 1024 - 8
Molecular structure of yeast RNA polymerase III: demonstration of the tripartite transcriptive system in lower eukaryotes; Valenzuela P et al.; Homogeneous RNA polymerase III (RNA nucleotidyltransferase III) has been obtained from yeast . The subunit composition of the enzyme was examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate . The enzyme is composed of 12 putative subunits with molecular weights 160,000, 128,000, 82,000, 41,000, 40,500, 37,000, 34,000, 28,000, 24,000, 20,000, 14,500, and 11,000 . The high-molecular-weight subunits and several of the smaller subunits of yeast RNA polymerase III are clearly different from those of enzymes I and II, indicating a distinct molecular structure . However, the molecular weights of some of the small subunits (41,000, 28,000, 24,000, and 14,500) appear to be identical to those of polymerases I and II . Thus, it is possible that the three classes of enzymes in yeast have some common subunits . As in other eukaryotes, yeast polymerase II is inhibited by relatively low concentrations of alpha-amanitin; however, contrary to what has been found in higher eukaryotes, yeast polymerase III is resistant (up to 2 mg/ml) to alpha-amanitin, while yeast polymerase I is sensitive to high concentrations of the drug (50% inhibition at 0.3 mg/ml) . These results establish the existence of RNA polymerase III in yeast and provide a structural basis for the discrimination of the three functional polymerases in eukaryotes.

Lipids, 1976 Apr, 11(4), 341 - 8
Extraction of lipids from yeast; Sobus MT et al.; Several methods for the extraction of lipids from intact yeast cells have been compared . Extraction of intact cells with methanol followed by methanol: benzene (1:1, v/v) and benzene resulted in the recovery of equal or greater amounts of polar and nonpolar lipids than obtained by other methods . A preparative method involving preincubation of cells with aqueous KOH followed by the treatment of the cellular residue as described above yielded slightly more steryl esters than was extracted from broken cell preparations.

Biochem J, 1976 Apr 1, 155(1), 155 - 61
State and accessibility of zinic in yeast alcohol dehydrogenase; Leskovac V et al.; 1 . Yeast alcohol dehydrogenase (EC 1.1.1.1) is inhibited in the presence of 1,10-phenanthroline . 2 . A conformational change in the enzyme's structure is induced by 1,10-phenanthroline, and is abolished in the presence of NADH . 1,10-Phenanthroline binds to the enzyme competitively with respect to NADH, with a stoicheiometry of 2 mol of 1,10-phenanthroline/144000g of enzyme . 3 . 1,10-Phenanthroline induces a time-dependent dissociation of Zn2+ from the enzyme, which is in correlation with its inhibitions . 4 . Spectrophotometric measurement indicates that the dissociation of half (2 zinc atoms/tetramer) of the total zinc content of the enzyme correlates with the full inhibition of its activity . Measurement of the tightly bound Zn2+ by atomic absorption photometry confirms this . 5 . A proposition is advanced that the tetrameric molecule of yeast alcohol dehydrogenase possesses an inherent asymmetry, with four monomeric subunits being arranged in two mutually symmetrical pairs.

Mol Gen Genet, 1976 Mar 22, 144(2), 119 - 25
Alterations in mitochondrial DNA of yeast which accompany genetically and environmentally controlled changes in rho- mutability; Lusena CV et al.; Alterations in the physical characteristics of mitochondrial DNA accompanied increased spontaneous mutability to cytoplasmic respiratory-deficiency in yeast . Two systems were used to modify mutation rates, one physiological, the other genetic . Cells in log phase were shown to be more mutable than cells in stationary phase, and glucose-repressed cells were shown to be more mutable than unrepressed cells . A nuclear gene which acts as a mitochondrial mutator was found to increase spontaneous mutation rate by a factor of ten . An increase in endogenous formation of G+G-rich fragments of mt-DNA accompanied a physiological state conducive to higher mutability, and it is proposed that increased in vivo digestion of A+T-rich regions is involved in these alterations . Greater nuclease(s) activity accompanied the presence of the mutator gene, and it is proposed that this gene is concerned with the regulation of nuclease activity or with repair mechanisms.

Arch Microbiol, 1976 Mar 19, 107(2), 205 - 6
Torulopsis spandovensis sp . n., a new yeast from beer; Henninger W et al.; A new species of the genus Torulopsis has been isolated from several different samples of German Pilsener Beer . A description of the new species is given.

Biochim Biophys Acta, 1976 Mar 18, 427(1), 20 - 7
Anomalous fluorescence of yeast 3-phosphoglucerate kinase; Nojima H et al.; The 3-phosphoglycerate kinase (EC 2.7.2.3) of yeast which contains two tryptophyl and eight tyrosyl residues per molecule, displayed an unusualy fluorescence emission spectrum with a maximum at 308 nm when excited at 280 nm . The emission peak shifted to 329 nm when excited at 295 nm . We could confirm that it was due to the efficient quenching of tryptophyl fluorescence as well as to the incomplete energy transfer from tyrosyl to tryptophyl residues . The average fluorescence quantum yield of this protein was 0.076 (excitation at 280 nm) and that of tryptophyl residues was 0.046 (excitation at 295 nm) . As the pH of the solution was lowered, the fluorescence intensity of phosphoglycerate kinase at 329 nm dramatically increased between pH 5 and 4, while the position of the peak remained unchanged . When denatured in 4 M guanidine hydrochloride, the protein showed two emission peaks, one at 343 nm and the other at 303 nm.

Eur J Biochem, 1976 Mar 16, 63(1), 249 - 62
Nuclear-magnetic-resonance study of the active-site structure of yeast phosphoglycerate kinase; Tanswell P et al.; The enzyme 3-phosphoglycerate kinase from yeast has been studied by observation of the proton nuclear magnetic resonance spectrum at 270 MHz using Fourier transform techniques . Difference spectroscopy was used to enhance the resolution and to identify specific ligand binding effects and conformational changes . Perturbations involving single protons of amino-acid residues could thus be detected despite the relatively high molecular weight of the protein (47000), particularly in the aromatic (6-9 ppm) and methylene (2-3 ppm) regions of the spectrum.

J Biol Chem, 1976 Mar 10, 251(5), 1464 - 70
Yeast DNA-dependent RNA polymerase I . A rapid procedure for the large scale purification of homogeneous enzyme; Valenzuela P et al.; A procedure has been developed for the rapid purification of large amounts of yeast RNA polymerase I (A) . The method involves batchwise treatment with phosphocellulose and DEAE-cellulose, ion filtration chromatography on DEAE-Sephadex, sucrose gradient centrifugation, and DNA-cellulose chromatography . The enzyme obtained is apparently homogeneous by sedimentation velocity analysis and has a specific activity of 300 nmol of UMP incorporated into RNA in 10 min per mg of protein . Between 30 and 45 mg of enzyme can be obtained in 5 days from 3.0 kg of yeast cells . The subunit composition of the enzyme was determined by polyacrylamide gel electrophoresis in the presence of 0.1% sodium dodecyl sulfate . The purified polymerase is composed of 11 putative subunits with molecular weights 185,000 (Ia), 137,000 (Ib), 48,000 (Ic), 44,000 (Id), 41,000 (Ie), 36,000 (If), 28,000 (Ig), 24,000 (Ih), 20,000 (Ii), 14,500 (Ij), and 12,000 (Ik) . Yeast polymerase I separates into two forms when subjected to gel electrophoresis under nondenaturing conditions . The main component which migrates faster contains all the subunits except the polypeptides Ic and If . The slow migrating component which is present in lower amounts contains all the subunits.

Biotechnol Bioeng, 1976 Mar, 18(3), 297 - 309
Daughter cells as an important factor in determining the physiological state of yeast populations; Vrana D; Cells of Candida utilis grown in a single-stage chemostat at D = 0.05, 0.1, 0.25, and 0.35 hr-1 were separated into a fraction of scar-bearing mother cells and a fraction of scar-free daughter cells . The scar-free cells were transferred into small batch cultures where the length of the maturation phase, changes in length and width of cells, specific growth rate, and specific rate of RNA and protein synthesis were examined for 5 hr . The daughter cells grown at D = 0.05 hr-1 were very small at the moment of separation from the mother cells (about one-third of the mother cell) . Their maturation phase (in a batch culture), at the beginning of which they attain the specific growth rate approaching the mumax of the strain used, lasts for 3 hr . On the other hand, daughter cells grown at D = 0.35 hr-1 are almost the same size as the mother cells at the moment of separation . After transfer to a batch culture they begin to bud almost immediately . Similarly, in their other morphological and physiological parameters they differ strikingly from immature daughter cells which are formed at low specific growth rates . The importance of these differences from the point of view of mathematical modeling of growth processes is discussed.

Nucleic Acids Res, 1976 Mar, 3(3), 523 - 35
Role of modified nucleosides in tRNA: effect of modification of the 2-thiouridine derivative located at the 5'-end of the anticodon of yeast transfer RNA Lys2; Sen GC et al.; Yeast tRNA Lys2 codes preferentially for AAA and contains a 2-thiouridine derivative (U) at the 5'-position of the anticodon . Removal of the 2-thio group from U by treatment with CNBr did not affect the amino acid accepting activity of the modified tRNA Lys2 . CNBr treated tRNA Lys2 was active in protein synthesis but with a much reduced efficiency . Although the modified tRNA Lys2 was recognized by elongation factor (EF) T, the EFT dependent binding to ribosomes to tRNA Lys2 (CNBr) was markedly decreased.

Nucleic Acids Res, 1976 Mar, 3(3), 631 - 9
Effect of excision of the Y-base on the interaction of tRNAPhe (yeast) with phenylalanyl-tRNA synthetase (yeast); Krauss G et al.; The interaction between tRNAPhe (yeast), from which the Y-base has been removed by acid treatment, and phenylalanyl-tRNA synthetase (yeast) has been investigated by fluorescence competition titrations and sedimentation velocity runs . The binding parameters are given under various ionic conditions . The tRNAPhe-Y still can occupy the specific binding sites on the enzyme . Compared to unmodified tRNAPhe, the binding constant is lowered by more than one order of magnitude . It can be concluded that the Y-base is not necessary for specific recognition of tRNAPhe by the cognate synthetase, it rather may represent a point of attachment for the synthetase.

Mol Gen Genet, 1976 Feb 27, 144(1), 29 - 37
A yeast mutant defective in the processing of 27S r-RNA precursor; Andrew C et al.; Among a group of 31 ts- yeast mutants screened electrophoretically for heat-sensitive synthesis of each stable RNA species, only mutant ts351 failed to accumulate 25S RNA at 36 degrees C . Pulse-labeling experiments at 36 degrees C showed that 35S and 27S precursors RNA and mature 18S r-RNA molecules are synthetized by ts351 cells but that 25S and 5.8S RNA species are not made and new 60S ribosomal sub-units are not assembled . The mutant is blocked at a specific point in r-RNA processing: the cutting of 27S to form 25S and 5.8S r-RNA.

Mol Gen Genet, 1976 Feb 27, 144(1), 21 - 7
Recombination and hydroxyurea inhibition of DNA synthesis in yeast meiosis; Simchen G et al.; Hydroxyurea (HU) inhibits the premeiotic DNA replication and the meiotic events that followed, namely readiness, recombination commitment, haploidisation, sporulation commitment and ascus formation . Short incubations with HU (2-4 hrs) during the premeiotic replication (i.e . starting between 3 and 6.5 hrs in sporulation medium) allow the resumption of the replication at a normal rate following the removal of the drug . The other meiotic events are similarly delayed by the approximate length of the treatment . In these experiments, intragenic recombination in ade2 reached a higher level than in the controls (x 1.3-2.0 in one pair of heteroalleles and x 3.0-4.0 in another pair) . The recombination response to short HU treatments was not observed for a pair of heteroalleles in ade2 that normally shows a high level of meiotic recombination (750 per 10(6) cells), nor was the response observed in a pair of heteroalleles in lys2 . HU treatments have almost no effect on sporulating cells from 8 hrs onwards . At 7-7.5 hrs the meiotic cells are very sensitive to the drug and even short treatments cause cell death and massive DNA degradation.

Biochim Biophys Acta, 1976 Feb 13, 422(2), 390 - 406
A kinetic study of homocitrate synthetase activity in the yeast Saccharomycopsis lipolytica; Gaillardin CM et al.; 1 . A rapid method for estimating the activity of the first enzyme of lysine biosynthesis in yeasts (acetyl-coenzyme A: 2-ketoglutarate C-acetyl transferase, EC 4.1.3.21) is described . 2 . In the wild type strain, the fixation of one substrate, S-acetyl coenzyme A, shows sigmoidal saturation kinetics . The initial rate experiments indicate that the reaction obeys an ordered mechanism, 2-ketoglutaric acid binding before S-acetyl coenzyme A . 3 . The activity is completely inhibited in vitro by lysine and by some lysine analogs, which all show cooperative binding and have an heterotropic effect on 2-ketoglutaric binding sites . A second class of affectors is found, including 2-aminoadipic acid, pipecolic acid and dipicolinic acid, which all affect the cooperativity of S-acetyl coenzyme A binding sites . 4 . Two types of mutations which modify these inhibition patterns without affecting the catalytic activity are described . One results in a desensitization towards lysine and lysine analogs only . The other entirely abolishes the susceptibility towards the second type of inhibitors, without affecting the susceptibility to lysine . 5 . No variations of the specific activity could be detected in the wild type strain at all; mutants showing an increased or a reduced activity were isolated . 6 . Our results do not support the existence of isoenzymes at the level of homocitrate synthetase in this yeast.

Biochemistry, 1976 Feb 10, 15(3), 560 - 5
Borate inhibition of yeast alcohol dehydrogenase; Smith KW et al.; Yeast alcohol dehydrogenase is inhibited competitively by borate with respect to NAD+ . An unusual mechanism of competitive inhibition prevails: the competition for the substrate NAD+ by borate and enzyme . The following evidence supports this conclusion . (1) Much greater inhibition is observed with respect to NAD+ as compared with NADH as substrates . (2) Borate decreases the equilibrium constant of the overall reaction in the direction of ethanol oxidation, therefore, borate enters directly into the overall reaction rather than merely decreases the effectiveness of the catalyst . (3) The Ki values for unrelated enzyme reactions are identical for NAD+ . (4) Stopped-flow experiments show burst kinetics only when NAD+ and borate are not premixed . (5) The Ki value is identical with the inverse of the borate-NAD+ complexation constant . (6) The pH dependence of the inhibitor demonstrates that only the B(OH)4-species is inhibiting . These results are consistent with the preferable binding of borate to NAD+ as compared with NADH . These two binding constants were found to be equal to 2000 +/- 60 and 130 +/- 8 M-1, respectively . In contrast to the liver enzyme, the yeast enzyme does not show pre-steady-state burst reactions in the reduction of NAD+ . This would indicate that the interconversion of ternary complexes is at least partially rate limiting for the yeast enzyme.

Eur J Biochem, 1976 Feb 2, 62(1), 65 - 76
Protein degradation and proteinases during yeast sporulation; Betz H et al.; During ascospore formation in Saccharomyces cerevisiae, at least 60-70% of the pre-existing vegetative protein was broken down at a rather constant rate until the time mature asci appeared . Under the same conditions in a non-sporulating haploid derived from the same strain the rate of protein degradation, although initially comparable to that of sporulating cells, decreased much more rapidly . Proteins synthesized at different times during sporulation had approximately the same degradation rates as the vegetative proteins . Similar rates of degradation were observed for the vegetative proteins in all fractions obtained from cell homogenates by differential centrifugation . Protein breakdown after transfer to sporulation medium was blocked by uncouplers and inhibitors of energy metabolism, and was partially inhibited by cycloheximide . Polyacrylamide gel electrophoresis, in the presence of sodium dodecylsulfate, of the proteins extracted from vegetative cells and from isolated asci and ascospores revealed that ascus formation was accompanied by a shift of the cellular proteins to a lower molecular weight . From several proteinase inhibitors tested, only tosyl-p-lysine chloromethylketone slightly reduced the rate of ascus formation . During sporulation the total activity of proteinase A increased more than twofold with a maximum at 18 h after transfer to sporulation medium . Total proteinase B activity showed a striking increase in the first hours after transfer to sporulation medium and after that remained constant throughout sporulation . The levels of carboxypeptidase Y and of the proteinase B inhibitor were not significantly altered during sporulation . The proteinases and the proteinase B inhibitor were present within the mature ascospore . The proteinases from both vegetative and sporulating cells were eluted with the same ionic strength from DEAE-Sephadex, and they were undistinguishable in their sensitivity to different proteinase inhibitors . No additional proteolytic activities could be detected in sporulating cells using 3H-labelled denatured yeast protein as a substrate.

Mol Gen Genet, 1976 Feb 2, 143(3), 253 - 9
Mitochondrial DNA in yeast recombination and subsequent modification following mating between a Grande and a suppressive Petite; Blamire J et al.; The fate of mitochondrial DNA, following mating between a grande and suppressive petite of Saccharomyces cerevisiae, has been followed for up to 60 generations . The buoyant density of the mitochondrial DNA was seen to change in a manner explicable by a combination of recombination and subsequent modification phenomena whilst the suppressivity of the petite zygotic clones always remained high.These findings are consistent with current models of mitochondrial DNA metabolism in which petite strains have been observed to undergo deletion and reamplification of certain parts of their genomes.

Can J Microbiol, 1976 Feb, 22(2), 213 - 20
The accumulation of succinate by the yeast Brettanomyces bruxellensis; Sanfacon R et al.; The metabolism of Brettanomyces bruxellensis was investigated to determine the metabolic block responsible for the accumulation of acetate seen in cultures of this yeast . In glucose-grown cultures the major non-volatile intracellular organic acide was succinic acid . These cultures also had low levels of succinic dehydrogenase (succinate dehydrogenase, EC 1.3.99.1) and did not produce CO2 from the carbons of ethanol . It was concluded that a block in the oxidation of ethanol occurred at the level of succinic dehydrogenase . If glucose-grown cultures were transferred to ethanol medium, the block in the metabolism of ethanol was partially overcome; the level of succinic dehydrogenase increased, the concentration of the intracellular succinate decreased, and CO2 could be produced from C-1 of ethanol.

Mutat Res, 1976 Feb, 34(2), 187 - 94
Counteracting effect of eosin and related dyestuffs on the production of respiration-deficient mutants in yeast by 4-nitroquinoline 1-oxide; Nagai S; Production of respiration-deficient (rho-) mutants under growing conditions in a strain of Saccharomyces chevalieri by 4-nitroquinoline 1-oxide (4NQO), a potent carcinogen, reached 100% . The mutation frequency was considerably reduced when eosin Y was applied in various combinations with 4NQO . The counteracting effect was slight when eosin Y was applied concurrently with 4NQO, but was very strong and persistent when eosin Y was impregnated into the yeast cells before their exposure to 4NQO . Eosin B, erythrosin B and uranin also showed more or less counteracting effects agains 4NQO in producing the rho- mutants . Possible mechanisms for the counteracting effects of these dyestuffs against 4NQO are discusses in relation to antimutagenesis and chemotherapeutic interference.

Biochem J, 1976 Feb 1, 153(2), 423 - 8
The association of yeast phosphoglycerate kinase (EC 2.7.2.3); Spragg SP et al.; 1 . A mol.wt . of 40030 +/- 830 has been estimated for phosphoglycerate kinase in concentrations less than 0.1 g/100 cm3 comparing favourably with expected values from X-ray diffraction measurements by 10% lower than the previously reported molecular weights made at higher concentrations . 2 . The so20w, was estimated to be 3.12(+/-0.02)x10(-13)s and the coefficient had a low concentration dependency giving a g value (concentration-dependency) of 2.3 +/- 1.6cm3 .g-1 . This agrees with previous qualitative observations . 3 . By using fluctuation-intensity spectroscopy, the D20,w was estimated to be 7.4(+/-0.2)x10(-11)m2.s-1, and this was indistinguishable from the D20,w calculated from ultracentrifuge results . The water of hydration was estimated to be 0.46 g/g of protein . 4 . It is inferred from the estimates that phosphoglycerate kinase associates with an interaction coefficient at 20 degrees C for monomer/dimer of between 10 and 12 cm3.g-1 . 5 . The ratio of molecular asymmetry (a/b) was estimated to be 2.5+/-0.2 from the values of D20,w and water of hydration . This compares favourably with the ratio from the overall dimensions estimated from X-ray diffraction measurements.

Genetics, 1976 Feb, 82(2), 207 - 32
UV mutagenesis in radiation-sensitive strains of yeast; Lawrence CW et al.; The yeast Saccharomyces cerevisiae appears to possess a single mutagenic or "error prony" pathway for the repair of UV damage; rev1, rev2, rev3 (Lemontt 1971a), rad6, rad8, rad9 and rad18 (Lawrence et al . 1974; present results) . Strains carrying rad6 are the most sensitive to the lethal effects of UV light in this group and double mutants carrying rad6 and either rev1, rev3, rad9 or rad18 are no more sensitive than this single mutant strain, rev3 rad6 doubl- mutant diploids failed to show any UV-induced reversion of the normally highly reversion of the normally highly revertible ochre allele cycl-9, even though a total of more than 2.5 X 10(9) viable cells was examined, suggesting that strains of this kind are entirely UV-immutable; spontaneous revertants could be recovered, however.-The rad6 and rev3 gene products would appear to be necessary for all kinds of mutagenic events at all sites within the genome, but the products of the other genes that act in the "error-prone" pathway have a more restricted role and are involved in the production of only some kinds of mutations . It is suggested that such selectivity arises from the interaction of some repair enzymes with specific nucleotide sequences.

Genetics, 1976 Feb, 82(2), 187 - 206
Regulation of mating and meiosis in yeast by the mating-type region; Kassir Y et al.; A supposed sporulation-deficient mutation of Saccharomyces cerevisiae is found to affect mating in haploids and in diploids, and to be inseparable from the mating-type locus by recombination . The mutation is regarded as a defective a allele and is designated a* . This is confirmed by its dominance relations in diploids, triploids, and tetraploids . Tetrad analysis of tetraploids and of their sporulating diploid progeny suggests the existence of an additional locus, RME, which regulates sporulation in yeast strains that can mate . Thus the recessive homozygous constitution rme/rm- enables the diploids a*/alpha, a/a*, and alpha/alpha to go through meiosis . Haploids carrying rme show apparent premeiotic DNA replication in sporulation conditions . This new regulatory locus is linked to the centromere of the mating-type chromosome, and its two alleles, rme and RME, are found among standard laboratory strains.

Mutat Res, 1976 Feb, 38(1), 43 - 52
The induction of mutation in yeast by hydrogen peroxide; Thacker J et al.; The inactivation and mutation to respiratory deficiency of yeast cells by H2O2 are shown to vary progressively with the phase of cell growth, with a sharp transition occurring as the cells complete logarithmic growth . Respiratory deficient mutants isolated from the wild-type population are of two types, one of which is much more sensitive to H2O2 but forms only a small fraction of the mutant sub-population . Based upon the response of the more resistant type, mutation frequency increases appear to result from selection of pre-existing mutants in log phase populations, while induction occurs in stationary phase cells . The induced mutation frequency fits a (dose)2 relationship, but the frequency is depressed when the dose is high (or number of cells treated is low) . All the induced mutants are extranuclear and of the resistant type, and show a wide range of suppressiveness in crosses to respiratory competent cells . This may indicate mitochondrial DNA is altered to different extents by H2O2; by the same criterion, the spontaneously occurring H2O2 -sensitive mutants retain a large amount of mitochondrial DNA information, in agreement with their colonial morphology . A small increase in forward mutation of nuclear genes was also found after H2O2 treatment . Parallels are drawn between the response of yeast cells to ionising radiation and to H2O2, and it is suggested that radical action may be involved in inactivation and mitochondrial genome mutation induced by both agents.

Mutat Res, 1976 Feb, 34(2), 195 - 200
A protective effect of caffeine on the ethidium induced petite mutation in yeast; Hixon SC et al.; A prerequisite for petite induction by ethidium bromide (EB) is an initial covalent attachment of the drug to cytoplasmic DNA . This DNA modification is thought to initiate repair processes . The repair inhibitor, caffeine, provided a protective effect against the ethidium induced petite mutation at caffeine concentrations known to inhibit the repair of UV damage in cytoplasmic DNA (Fig . 1) . Mitochondrial DNA isolated from yeast exposed to EB in vivo was not as degraded in the presence of both drugs as with EB alone (Fig . 2).

Biochem J, 1976 Feb 1, 153(2), 145 - 9
Yeast phosphoglycerate mutate . Cyanogen bromide cleavage and amino acid sequence of an active-site peptide; Fothergill LA et al.; The molecular weight and amino acid composition of phosphoglycerate mutase from yeast were determined . CNBr cleavage produced a large (190-residue) fragment and a small (60-residue) fragment . Tryptic and chymotryptic peptides derived from the large fragment were fractionated by ion-exchange chromatography . Peptides from two histidine-containing regions were isolated and the amino acid sequences were determined . Correlation of these data with X-ray-crystallographic evidence shows that the histidine residue in the sequence Arg-Leu Asn-Glu-Arg-His-Tyr-Gly-Asp-Leu-Glu-Gly-Lys is located at the active site.

Genetics, 1976 Feb, 82(2), 251 - 72
Isolation and characterization of amber suppressors in yeast; Liebman SW et al.; Nonsense suppressors were obtained in a haploid yeast strain containing eight nutritional mutations, that are assumed to be amber or ochre, and the cyc1-179 amber mutation that has a UAG codon corresponding to position 9 in iso-1-cytochrome c . Previous studies established that the biosynthesis and function of iso-1-cytochrome c is compatible with replacements at position 9 of amino acids having widely different structures (Stewart and Sherman 1972) . UV-induced revertants, selected on media requiring the reversion of one or two of the amber nutritional markers, were presumed to contain a suppressor if there was the unselected reversion of at least one other marker . The 1088 suppressors that were isolated could be divided into 78 phenotypic classes . Only 43 suppressors of three classes caused the production of more than 50% of the normal amount of iso-1-cytochrome c in the cyc1-179 strain . Genetic analyses indicated that all of these highly efficient amber suppressors are allelic to one or another of the eight suppressors which cause the insertion of tyrosine at ochre (UAA) codons (Gilmore, Stewart and Sherman 1971) . Furthermore, only tyrosine has been identified at position 9 in iso-1-cytochrome c in cyc1-179 strains suppressed with these efficient amber suppressors.

Genetics, 1976 Feb, 82(2), 233 - 49
Inhibition of growth by amber suppressors in yeast; Liebman SW et al.; Strains of the yeast Saccharomyces cerevisiae that contain highly efficient amber (UAG) suppressors grow poorly on nutrient medium, while normal or nearly normal growth rates are observed when these strains lose the supressors or when the suppressors are mutated to lower efficiencies . The different growth rates account for the accumulation of mutants with lowered efficiencies in cultures of strains with highly efficient amber suppressors . Genetic analyses indicate that one of the mutations with a lowered efficiency of suppression is caused by an intragenic mutation of the amber supressor . The inhibition of growth caused by excessive suppression is expected to be exacerbated when appropriate suppressors are combined together in haploid cells if two suppressors act with a greater efficiency than a single suppressor . Such retardation of growth is observed with combinations of two UAA (ochre) suppressors (Gilmore 1967) and with combinations of two UAG suppressors when the efficiencies of each of the suppressors are within a critical range . In contrast, combinations of a UAA suppressor and a UAG suppressor do not affect growth rate . Apparently while either excessive UAA or excessive UAG suppression is deleterious to yeast, a moderate level of simultaneous UAA and UAG suppression is not.

Biochemistry, 1976 Jan 27, 15(2), 257 - 61
Mechanism of yeast cytochrome b2 action . II . Steady-state kinetics of oxalate inhibition; Blazy B et al.; From a careful steady-state kinetic study it is shown that the inhibition of L-lactate oxidation by cytochrome b2 with ferricyanide as acceptor is of the mixed competitive-noncompetitive type, indicating the formation of an active ternary complex between enzyme, substrate, and inhibitor . With a large excess of acceptor, the simplest formal mechanism consistent with all available data is: E + L equilibrium EL; E + S equilibrium ES leads to EP leads to E + P; ES + L equilibrium ESL leads to EPL leads to EL + P, where L is oxalate, S is L-lactate, P is pyruvate, and E is enzyme . The inhibition kinetics together with the rate constants for oxalate binding to free enzyme (Thusius, D., Blazy, B., and Baudras, A . (1976), Biochemistry, preceding paper in this issue) and recent steady-state experiments on L-lactate deuterated at C-2 (Lederer, F . (1974), Eur . J . Biochem, 46, 393) lead to estimates of some of the elementary rate parameters in the above scheme . As in the case of oxalate (see Thusius et al . reference above), the association rate constant for substrate binding (1.1 x 10(5) M-1 sec-1) is much smaller than a diffusion-controlled value . Our results also imply that dissociation of complex EP to free enzyme and pyruvate is partially rate limiting for the overall reaction.

Biochemistry, 1976 Jan 27, 15(2), 250 - 6
Mechanism of yeast cytochrome b2 action . I . Thermodynamics and relaxation kinetics of the interaction between cytochrome b2 and oxalate; Thusius D et al.; Oxalate is the strongest known inhibitor of yeast cytochrome b2 activity . We have used spectrophotometric titration, temperature-jump relaxation, and calorimetry in an investigation of the interaction between enzyme and inhibitor . The titration data are consistent with noncooperative binding to one site per subunit . This conclusion is corroborated by temperature-jump results which reveal a single relaxation phenomenon which obeys second-order kinetics . Further evidence for a simple binding reaction enthalpy estimated from relaxation amplitudes is in good agreement with the value obtained directly with batch calorimetry . The forward and reverse rate constants evaluated from the temperature-jump experiments are, respectively, 1 x 10(4) M-1 sec-1 and 15 sec-1 . Although considerably smaller than a diffusion-controlled value, the forward rate constant is characterized by an unusually small activation energy of approximately 3 kcal/mol . This, together with a large unfavorable association activation entropy of -30 eu, suggests that oxalate diffuses freely to the active site, but only a small fraction of the collisions are productive due to severe steric requirements.

J Biol Chem, 1976 Jan 25, 251(2), 257 - 69
Studies on cytochrome oxidase . Partial resolution of enzymes containing seven or six subunits, from yeast and beef heart, respectively; Phan SH et al.; Highly active, essentially homogeneous, preparations of ferrocytochrome c oxidase (EC 1.9.3.1) have been obtained from both yeast and beef heart by extraction with cholate, fractionation with ammonium sulfate, and replacement of cholate by Tween 20 . The molecular weights of the resultant proteins equal 260 +/- 23 X 10(3) and 205 +/- 10(3); they contain seven and six different polypeptide subunits, respectively, all in equimolar amounts, with apparent molecular weights of 42.4, 34.1, 24.7, 14.6, 14.6, 12.3, 10.6 X 10(3), and 47.5, 20.4, 14.5, 14.5, 13.0, 11.0 X 10(3), respectively . By means of apolar chromatography on L-leucine coupled to agarose these enzymes can be stripped of their largest subunit(s) resulting in preparations with molecular weights of 170 +/- 17 X 10(3) and 124 +/- 20 X 10(3), and containing only five polypeptides, with the largest remaining one (molecular weight congruent to 20 X 10(3)) present in less than stoichiometric amounts . This interconversion and subunit removal has been monitored by exclusion chromatography, four systems of acrylamide gel electrophoresis--some with the protein labeled with 125I under denaturing conditions--isoelectric focusing, and hydrodynamic methods . It has virtually no effect on heme a and copper content and on the catalytic parameters of the enzymes . We conclude that subunits I and II in enzymes from fungal, and subunit I in those from animal, sources are dispensable for the catalysis of the oxidation of ferrocytochrome c by, and are probably not essential for the attatchment of prosthetic groups to, these proteins.

C R Acad Sci Hebd Seances Acad Sci D, 1976 Jan 5, 282(1), 123 - 5
{Oxygen consumption by the yeast-like and filamentous forms of Sporothrix schenckii as measured by polarography}; Trefouel MJ; The study of the oxygen uptake by cultures of Sporothrix schenckii as measured with the Clark electrode has shown that when the fungus was grown in a liquid medium, the atmospheric oxygen went into solution very slowly even when the liquid was rapidly stirred . The partial oxygen pressure was very small after some days of culture (no more than 2 or 3% expressed as the saturated value) . Hence, it is postulated that the linear part of the growth curve is due to the dissolved oxygen acting as a limiting factor . When the oxygen uptake by filaments, conidia, or yeasts isplotted against the time the curve variations follow the transformations of the fungus.

Eur J Biochem, 1976 Jan 2, 61(1), 27 - 41
Localization in yeast mitochondrial DNA of mutations expressed in a deficiency of cytochrome oxidase and/or coenzyme QH2-cytochrome c reductase; Slonimski PP et al.; 1 . Three methods are described for the genetic analysis of yeast cytoplasmic mutants (mit- mutants) lacking cytochrome oxidase or coenzyme QH2-cytochrome c reductase . The procedures permit mutations in mitochondrial DNA to be mapped relative to each other and with respect to drug-resistant markers . The first method is based upon the finding that crosses of mit- mutants with some but not other isonuclear q- mutants lead to the restoration of respiratory functions . Thus a segment of mitochondrial DNA corresponding to a given mit- mutation or to a set of mutations can be delineated . The second method is based on the appearance of wild-type progeny in mit- X mit- crosses . The third one is based on the analysis of various recombinant classes issued from crosses between mit-, drug-sensitive and mit+, drug-resistant mutants . Representative genetic markers of the RIBI, OLII, OLI2 and PAR1 loci were used for this purpose . 2 . The three methods when applied to the study of 48 mit- mutants gave coherent results . At least three distinct regions on mitochondrial DNA in which mutations cause loss of functional cytochrome oxidase have been established . A fourth region represented by closely clustered mutants lacking coenzyme QH2-cytochrome c reductase and spectrally detectable cytochrome b has also been studied . 3 . The three genetic regions of cytochrome oxidase and the cytochrome b region were localized by the third method on the circular map, in spans of mitochondrial DNA defined by the drug-resistant markers . The results obtained by this method were confirmed by analysis of the crosses between selected mit- mutants and a large number of q- clones whose retained segments of mitochondrial DNA contained various combinations of drug-resistant markers . 4 . All the genetic data indicate that the various regions studied are dispersed on the mitochondrial genome and in some instances regions or clusters of closely linked mutations involved in the same respiratory function (cytochrome oxidase) are separated by other regions which code for entirely different functions such as ribosomal RNA.

Antonie Van Leeuwenhoek, 1976, 42(4), 533 - 40
Taxonomical examination and characterization of a methanol-utilizing yeast; Craveri R et al.; The morphological, cultural, and physiological characteristics are described of a yeast, LI70, which uses methanol as its source of energy and carbon; these characteristics have made it possible to identify the strain as Candida boidinii Ramirez . The identification was confirmed by a DNA-DNA genetic homology of 99.43% with the type strain of C . boidinii . Strain LI70 is not pathogenic.

Antonie Van Leeuwenhoek, 1976, 42(4), 523 - 32
Comparison between the yeast flora of Middle Eastern and Western European soft drinks; Sand FE et al.; Samples of a carbonated orange drink, raw materials, and intermediate products originating from 6 Iraqi bottling plants were examined . 69 drinks, 4 flavoured syrups and 19 simple syrups contained yeasts, whereas all samples from one plant and all samples of beverage base were free from viable yeasts . From the orange drink 2 species were isolated viz . Saccharomyces montanus and Torulopsis stellata . The following species were present in simple syrup: Hansenula anomala, Sacch . bisporus var . mellis, T . candida and T . stellata . Sacch . bisporus var . mellis was also isolated from favoured syrup . Representative strains were submitted to routine growth tests at reduced oxygen tension, at reduced water activity and on solid soft-drink media containing various amounts of anti-microbially active benzoic acid at pH 3.0 . The results are discussed and compared to those obtained in European soft drinks.

Acta Biol, 1976, 27(2-3), 101 - 6
Carbohydrates from hydrocarbons . II . Free and bound sugars from yeast cells grown on n-hexadecane; Jwanny EW et al.; Candida lipolytica (strain 10) was grown on an n-hexadecane medium with and without yeast extract . The harvested dry cells were weighed at various stages of growth . The free sugars from the cultures were obtained by Soxhlet extraction with 85% ethyl alcohol . Further qualitative and quantitative analyses of free monosaccharides in the concentrated alcoholic extracts were made by paper chromatography . Glucose was the only free monosaccharide that could be identified at various stages of growth . The chromatographic analysis of the acid-hydrolyzed yeast cells indicated the presence of glucose and mannose as dominant bound sugars; galactose and xylose were present in minor quantities . In the harvested dry cells from the yeast extract-containing medium, in general, greater amounts of bound sugars were present.

Acta Biol Med Ger, 1976, 35(11), 1443 - 53
{Kinetic properties of enzymes in particular of yeast alcohol dehydrogenase following their adsorption on polyaminomethylstyrene}; Schopp W et al.; The adsorption of 8 enzymes to polyaminomethylstyrene was studied . While lactate dehydrogenase, alkaline phosphatase and glucose-6-phosphate dehydrogenase exhibit a relatively low affinity to the carrier, alcohol dehydrogenase, glutamate dehydrogenase and urease were found to form stabile complexes with the polymer that are enzymatically active . Adsorbed urease and beta-hydroxybutyrate dehydrogenase, are still active after several weeks; the other preparations lose their activity soon . It can be shown by the example of yeast alcohol dehydrogenase that the activity loss following adsorption is caused possibly by a process of reorientation of already bound enzyme molecules or by the increasing enzyme coverage of the carrier, with the active centres becoming more and more inaccessible for the substrate . During the substrate conversion catalysed by the alcohol dehydrogenase-polyaminomethylstyrene complex, a small amount of the enzyme is again detached from the carrier . The activity rises to a certain extent in the supernatant but drops to zero again . The stability of the adsorbed urease is distinctly increased compared with the dissolved enzyme . For the pH optimum and the KM value there are no differences between the two preparations . Continuous application of polyaminomethylstyrene-bound beta-hydroxybutyrate dehydrogenase and urease, respectively, in a column shows that both preparations have unchanged enzymatic activities even after running times of 5 and 24 days, respectively.

Acta Biochim Pol, 1976, 23(4), 321 - 4
On sulfhydrylation of O-acetylserine and O-acetylhomoserine in homocysteine synthesis in yeast; Paszewski A et al.; Considerable differences in the activities of cysteine and homocysteine synthase (EC 4.2.99.8), and in the ratio of these activities were observed in yeast strains representing different genera and species . This suggests that homocysteine synthesis directly from O-acetylhomoserine may predominate in some strains, whereas in the others homocysteine is formed from cysteine via cystathionine.

Folia Microbiol (Praha), 1976, 21(5), 384 - 90
Assimilation spectrum of the yeast Candida utilis 49 used for producing fodder yeast from synthetic ethanol; Sestakova M; Oxidizing and assimilating ability of the yeast Candida utilis 49 was tested with 21 different low-boiling organic compounds which come as components of raw synthetic ethanol . The highest yields of yeast dry weight were obtained with ethanol (72.0%), propanol (48.2%), ethyl acetate (43.4%) and acetic acid (34.2%) . To a minor extent, the yeast was capable of utilizing also 2-propanol, butanol and 2-butanol; it oxidized most of the compounds tested.

Folia Microbiol (Praha), 1976, 21(4), 306 - 14
Oxidation of methanol, formaldehyde and formic acid by methanol-utilizing yeast; Pilat P et al.; Methanol-utilizing yeast, Candida boidini 11 Bh, characterized by high tolerance to methanol during growth, displays even higher tolerance when the oxidation rate by intact cells is tested . Low respiration activity is found even at 22% v/v of methanol . The half-saturation constant was 17-18 mM . The half-saturation constants for the two oxidation intermediates, formaldehyde and formic acid were 3.5-4.0 an .d 30-33 mM, respectively . When applied together with standard concentration of methanol, very low concentrations of both intermediates stimulated the oxidation rate . These results are discussed in connection with the relationship between growth and oxidation, the tolerance to high concentrations of inhibitory products and the mechanism of inhibition.

Z Allg Mikrobiol, 1976, 16(2), 107 - 13
{Protein crystals and tubuli bundles in yeast cells . V . Enrichment of crystal and tubuli proteins during O2 limitation and anaerobiosis}; May R et al.; Cells of Saccharomyces carlsbergensis contain proteins assembling to crystals and bundles of tubules (tb) in the cyto- and karyoplasm by osmotic shock with hypertonic solutions . The cellular concentration of these proteins is regulated by oxygen pressure during growth . In cells grown at optimal aeration the protein level is low and crystals and tb cannot be induced . After a short period of O2-limitation or anerobic growth conditions the protein concentration increases and induction of crystals and tb is possible.

Arch Tierernahr, 1976 Jan, 26(1), 61 - 5
{Nutritional value of wine yeast for sheep and swine}; Schuler D et al.; A digestibility trials was carried out with male sheep and one with fattening pigs to investigate the digestibility of wine yeast . 4 two-year-old male sheep and 5 castrated male pigs (live weight approximately 80 kgs) were used as experimental animals . The following digestibility data (%) were established on the sheep: organic matter: 78.9; energy: 79.1; crude protein: 61.1; crude fat: 88.8; crude fibre: 88.8; NFE 86.1 . The corresponding data for the pigs were 55.4; 46.3; 22.7; 12.1; 92.7; 69.8 . Thus, the resulting energy concentration was approximately 630 EFr units or 405 EFs units and the content of digestible crude protein in the dry matter was about 16% for ruminants and 6% in the pigs.

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