S. cerevisiae

J Bacteriol, 1981 Oct, 148(1), 241 - 7
Proline transport in Saccharomyces cerevisiae; Lasko PF et al.; The yeast Saccharomyces cerevisiae is capable of utilizing proline as the sole source of nitrogen . Mutants of S . cerevisiae with defective proline transport were isolated by selecting for resistance to either of the toxic proline analogs L-azetidine-2-carboxylate or 3,4-dehydro-DL-proline . Strains carrying the put4 mutation are defective in the high-affinity proline transport system . These mutants could still grow when given high concentrations of proline, due to the operation of low-affinity systems whose existence as confirmed by kinetic studies . Both systems were repressed by ammonium ions, and either was induce by proline . Low-affinity transport was inhibited by histidine, so put4 mutants were unable to grow on a medium containing high concentrations of proline to which histidine has been added.

Chem Biol Interact, 1981 Oct, 37(1-2), 123 - 40
Toxicity, interstrand cross-links and DNA fragmentation induced by 'activated' cyclophosphamide in yeast; Fleer R et al.; Treatment of yeast cells with 4-hydroperoxy-cyclophosphamide (4-OOH-CP), the chemically activated form of cyclophosphamide, results in cell killing, induction of DNA interstrand cross-links and DNA fragmentation . Toxicity of 4-OOH-CP is greatly influenced by the cell's capacity of DNA dark-repair: genetic blocking of non-epistatic pathways of DNA repair results in an increase of sensitivity of several orders of magnitude . DNa primary lesions have been measured using a haploid, excision deficient, dTMP-uptaking mutant of S . cerevisiae . In this strain, a significant extent of DNA cross-linking can already be observed at a survival of 88% . At a concentration of 100 nmol/ml 4-OOH-CP, renaturability of DNA increases up to 12 h of drug exposure and drops to lower values upon further incubation . In contrast to the time course of renaturability, DNA double-strand breakage is seen at later stages of drug treatment and continuously increases as a function of incubation time . Whereas inactivation of cells and induction of strand breakage continue upon postincubation of cells, comparable effects are much less pronounced for DNA renaturability.

Biochim Biophys Acta, 1981 Sep 24, 665(3), 420 - 6
Characterization of phosphatidylserine synthase from Saccharomyces cerevisiae and a mutant defective in the enzyme; Nikawa JI et al.; The membrane fraction of exponentially growing cells of Saccharomyces cerevisiae was found to exhibit phosphatidylserine synthase activity . The enzyme was solubilized by Triton X-100 and chromatographed on a Sepharose 6B column . The enzyme had a pH optimum between 8.0 and 8.5 . The apparent Km values for CDPdiacylglycerol and L-serine were 0.12 and 13 mM, respectively . Triton X-100 stimulated the enzyme . Mg2+ or Mn2+ was required for the activity . Ca2+ was inhibitory at relatively low concentrations . The enzyme was highly specific to L-serine . Labeling experiments showed that the enzyme synthesized phosphatidylserine by transferring the phosphatidyl moiety to L-serine . A mutant of S . cerevisiae defective in phosphatidylserine synthase was isolated . The strain required ethanolamine for its growth . Ethanolamine could be substituted by choline or high concentrations of L-serine . The mutant showed normal levels of CDPdiacylglycerol-inositol 3-phosphatidyltransferase and phosphatidylethanolamine methyltransferase activities.

Biochemistry, 1981 Sep 15, 20(19), 5403 - 11
Guanidine hydrochloride induced unfolding of yeast iso-2 cytochrome c; Nall BT et al.; The properties of the guanidine hydrochloride induced unfolding transition of iso-2 cytochrome c (iso-2) from Saccharomyces cerevisiae have been investigated by using kinetic and equilibrium techniques and have been compared with previously published studies of horse cytochrome c, which differs from iso-2 by 46% in amino acid sequence . Measurements of absorbance in the ultraviolet and visible spectral regions as a function of guanidine hydrochloride concentration give superimposable equilibrium transition curves with a midpoint of 1.15 M at pH 7.2 and 20 degrees C . A two-state analysis of the equilibrium data gives a Gibbs free energy of unfolding of 3.1 kcal/mol at 20 degrees C in the absence of denaturant . This agrees well with the predicted difference in stability between S . cerevisiae iso-2 and horse cytochrome c estimated from the free energies of transfer of buried hydrophobic groups . Three kinetic phases associated with folding can be detected throughout most of the transition zone . Two of the phases are detected by stopped-flow mixing experiments . The third phase is over within the mixing time of the flow experiments but is detectable by temperature jumps . At 20 degrees C, pH 7.2, the slowest phase (T1) is in the 20-100-s time range, the middle phase (T2) is in the 0.1-3-s range, and the fastest phase (T3) is on the order of 1 ms . For the reactions observed in the stopped flow (T1 and T2), a simplified three-state mechanism can be used to predict quantitatively the relative amplitudes of the phases and the equilibrium unfolding curve from the observed time constant data . Previously this same mechanism has been successful in describing the folding reactions of horse cytochrome c {Hagerman, P . J . (1977) Biopolymers 16, 731} . We suggest that the qualitative features of protein folding reactions may be conserved among homologous proteins.

Mol Cell Biol, 1981 Sep, 1(9), 836 - 42
Genetic complementation of the Saccharomyces cerevisiae leu2 gene by the Escherichia coli leuB gene; Storms RK et al.; The leucine operon of Escherichia coli was cloned on a plasmid possessing both E . coli and Saccharomyces cerevisiae replication origins . This plasmid, pEH25, transformed leuA, leuB, and leuD auxotrophs of E . coli to prototrophy; it also transformed leu2 auxotrophs of S . cerevisiae to prototrophy . beta-Isopropylmalate dehydrogenase was encoded by the leuB gene of E . coli and the leu2 gene of yeast . Verification that the leuB gene present on pEH26 was responsible for complementing yeast leu2 was obtained by isolating in E . coli several leuB mutations that resided on the plasmid . These mutant leuB- plasmids were no longer capable of complementing leu2 in S . cerevisiae . We conclude that S . cerevisiae is capable of transcribing at least a portion of the polycistronic leu operon of E . coli and can translate a functional protein from at least the second gene of this operon . The yeast Leu+ transformants obtained with pEH25, when cultured in minimal medium lacking leucine, grew with a doubling time three to four times longer than when cultured in medium supplemented with leucine.

Nucleic Acids Res, 1981 Aug 11, 9(15), 3621 - 40
Secondary structure comparisons between small subunit ribosomal RNA molecules from six different species; Zwieb C et al.; Secondary structure models are presented for three pairs of small subunit ribosomal RNA molecules . These are the 16S rRNA from E . coli cytoplasmic and Z . mays chloroplast ribosomes, the 18S rRNA from S . cerevisiae and X . laevis cytoplasmic ribosomes, and the 12S rRNA from human and mouse mitochondrial ribosomes . Using the experimentally-established secondary structure of the E . coli 16S rRNA as a basis, the models were derived both by searching for primary structural homology between the three classes of sequence (12S, 16S, 18S), and also by searching for compensating base changes in putative helical regions of each pair of sequences . The models support the concept that secondary structure of ribosomal RNA has been extensively conserved throughout evolution, differences in length between the three classes of sequence being accommodated in distinct regions of the molecules.

J Bioenerg Biomembr, 1981 Aug, 13(3-4), 141 - 8
Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria; Pasquali P et al.; Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms of KM, although a decrease of Vmax is sometimes observed . Experiments with submitochondrial particles from a UQ-deficient mutant of S . cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III.

Cell, 1981 Aug, 25(2), 525 - 36
Distinct repressible mRNAs for cytoplasmic and secreted yeast invertase are encoded by a single gene; Perlman D et al.; We have studied regulation of invertase putative structural genes (SUC) in S . cerevisiae and the synthetic relationship between secreted, glycosylated invertase (E.C.3.2.1.26) and the cytoplasmic, nonglycosylated form of the enzyme . Using immunoprecipitation and gel electrophoresis, we have analyzed invertase polypeptides and glycopeptides synthesized in vitro and in vivo . Analysis of size-fractionated mRNA from a SUC2 strain has shown that three mature, catabolite-repressible mRNA species direct the in vitro synthesis of three invertase polypeptides that have differing molecular weights . Two of these polypeptides, P63 and P62 (63 and 62 kd), are larger than the polypeptides of the secreted enzyme and are cotranslationally processed by microsomal membranes in vitro to yield secreted invertase glycopeptides (GP90 and GP87) . The smallest polypeptide, P60 (60 kd), which comigrates electrophoretically with cytoplasmic invertase, is not processed . Posttranslationally, a microsomal-membrane detergent extract removes approximately 20 aminoacids from P62 but not from P60 . In vitro translations of mRNAs from a genetically confirmed suc3 mutant strain, from the parental SUC3 strain and from derivative meiotic segregants have shown that the three polypeptides (and therefore three mRNA species) are encoded by one gene . Analysis of in vivo radiolabeled invertase from the same SUC3 and suc3 strains has verified that the SUC3 locus contains the structural gene for secreted and cytoplasmic invertase . Through the derepressed synthesis of multiple primary or processed transcripts, the SUC2 and SUC3 genes are regulated to produce multiple invertase polypeptides . The larger two polypeptides appear to be processed and secreted to yield glycosylated invertase, while the smallest remains in the cytoplasm.

Cell, 1981 Aug, 25(2), 451 - 60
Compartmentalized assembly of oligosaccharides on exported glycoproteins in yeast; Esmon B et al.; Temperature-sensitive secretory mutants (sec) of S . cerevisiae have been used to evaluate the stages and localization of glycoprotein oligosaccharide synthesis . At the nonpermissive growth temperature (37 degrees C), the sec mutants accumulate secretory organelles and glycoproteins . Histochemical staining and thin-section electron microscopy reveal that the secreted glycoprotein, acid phosphatase, is contained within one of three distinct organelles that accumulates in different mutants: ER; Golgi-like structures called Berkeley bodies; and 80--100 nm vesicles . When produced at 37 degrees C, invertase and acid phosphatase have less carbohydrate in the mutants that accumulate ER than in other mutants, or than in the wild-type strain . External invertase migrates on SDS-polyacrylamide gels as a heterogeneous species with an apparent molecular weight of 100 to 140 kd . Radiolabeled invertase, immunoprecipitated from extracts of ER-accumulating mutant cells, migrates as a set of three discrete protein species with apparent molecular weights of 79, 81, and 83 kd; the other mutants produce a form more like the secreted enzyme . In each case, removal of N-glycosidically linked oligosaccharides by treatment with endoglycosidase H produces a discrete species that migrates as a protein of 61 kd . Immunochemical analysis of bulk glycoprotein accumulated in the mutants suggests that a major portion of the N-linked oligosaccharide, the outer chain, is added after material passes from the ER.

Antimicrob Agents Chemother, 1981 Aug, 20(2), 184 - 9
Physiological response of Saccharomyces cerevisiae to 15-azasterol-mediated growth inhibition; Rodriguez RJ et al.; We studied 15-aza-24-methylene-8,14-cholestadiene-3 beta-ol (15-azasterol) inhibition of Saccharomyces cerevisiae growth . Exposure to sublethal concentrations of this drug caused S . cerevisiae cells to undergo a transient period of inhibition at midlog phase . During growth inhibition the turbidity of each culture remained constant, as did the total cell number . Although the proportion of viable cells in cultures decreased from 90 to 12% during inhibition, methylene blue staining showed that less than 40% of the cells underwent metabolic inactivation . We monitored adenosine triphosphate levels throughout the inhibition cycle, and these levels followed kinetics identical to cell growth kinetics . After overcoming inhibition, cellular lipid extracts revealed the presence of a modified form of 15-azasterol . It appeared that the yeast cells were able to overcome 15-azasterol inhibition by an inactivating transmethylation reaction involving S-adenosylmethionine.

Biochemistry, 1981 Jul 7, 20(14), 4217 - 23
Identification of 3,4-dihydroxy-5-hexaprenylbenzoic acid as an intermediate in the biosynthesis of ubiquinone-6 by Saccharomyces cerevisiae; Goewert RR et al.; The mutant strain of Saccharomyces cerevisiae E3-24 is unable to synthesize ubiquinone-6 . When this mutant is grown in the presence of p-hydroxy{U-14C}benzoate or p-hydroxy{carboxy-14C}benzoate, a radioactive compound accumulates . This new metabolite has been isolated and identified as 3,4-dihydroxy-5-hexaprenylbenzoate (3,4-DHHB) . Aerobically grown prototrophic strains of S . cerevisiae were found to contain only low levels of this compound . When strain X963-18C, blocked at homoserine O-transacetylase (in methionine biosynthesis), was deprived of methionine, ubiquinone biosynthesis ceased, and 3,4-DHHB was observed to accumulate . This suggested that S-adenosylmethionine (SAM) could be the methyl donor for 3,4-DHHB . Restoration of methionine to the cultures released this block and resulted in the conversion of 3,4-DHHB to ubiquinone-6, demonstrating a precursor--product relationship . The identification of 3,4-DHHB as an intermediate in ubiquinone biosynthesis in yeast establishes an alternate pathway for ubiquinone biosynthesis in eukaryotes.

Proc Natl Acad Sci U S A, 1981 Jul, 78(7), 4466 - 70
Expression and processing of bacterial beta-lactamase in the yeast Saccharomyces cerevisiae; Roggenkamp R et al.; The mode of expression in Saccharomyces cerevisiae of the bacterial antibiotic resistance gene coding for beta-lactamase (EC 3.5.2.6) is described . Yeast transformants, containing hybrid plasmid pMP78-1 consisting of pBR325 in a 2-micrometers DNA vector, synthesize an active beta-lactamase protein . The enzyme was purified about 100-fold over crude extracts . With regard to activity, molecular weight, and binding to specific antibodies the yeast beta-lactamase was indistinguishable from the purified enzyme from Escherichia coli . Because the bacterial enzyme is synthesized as a preprotein with subsequent maturation, the results suggest that S . cerevisiae is able to convert the preprotein to the mature beta-lactamase . This was confirmed by in vitro experiments showing that the bacterial preprotein can be processed by crude extracts of S . cerevisiae.

Cell, 1981 Jun, 24(3), 819 - 28
Dispersed 5S RNA genes in N . crassa: structure, expression and evolution; Selker EU et al.; The 5S RNA genes (5S genes) in N . crassa are not tandemly arranged or tightly clustered as in other eucaryotes that have been examined . 55 RNA or cloned 5S DNA hybridizes to at least 30 different restriction fragments of Neurospora DNA . Of 34 5S DNA clones examined, each contains a single 5S gene . Saturation hybridization analyses indicate that there are about 100 copies of 5S genes in the genome of this organism . We have partially or completely sequenced the 5S region of 15 clones . Both identical and highly divergent 5S coding regions were found . Nine are of one type (alpha) . The other six include four different types (beta, beta', gamma and delta) which differ from each other and from the alpha genes to various degrees . Eleven of 15 genes have distinct flanking regions . Analysis of Neurospora 5S RNA showed that it consists of one principal species which matches the alpha-type gene sequence . Additional 5S species corresponding to the less abundant 5S gene types were also detected . The pattern of nucleotide substitutions between the predicted Neurospora 5S RNAs and between these and S . cerevisiae 5S RNA suggests that a particular 5S RNA secondary structure occurs in vivo and is conserved.

Genetics, 1981 May, 98(1), 25 - 40
Mutants of yeast defective in sucrose utilization; Carlson M et al.; Utilization of sucrose as a source of carbon and energy in yeast (Saccharomyces) is controlled by the classical SUC genes, which confer the ability to produce the sucrose-degrading enzyme invertase (Mortimer and Hawthorne 1969) . Mutants of S . cerevisiae strain S288C (SUC2+) unable to grow anaerobically on sucrose, but still able to use glucose, were isolated . Two major complementation groups were identified: twenty-four recessive mutations at the SUC2 locus (suc2-); and five recessive mutations defining a new locus, SNF1 (for sucrose nonfermenting), essential for sucrose utilization . Two minor complementation groups, each comprising a single member with a leaky sucrose-nonfermenting phenotype, were also identified . The Suc2 mutations isolated include four suppressible amber mutations and five mutations apparently exhibiting intragenic complementation; complementation analysis and mitotic mapping studies indicated that all of the suc2 mutations are alleles of a single gene . These results suggest that SUC2 encodes a protein, probably a dimer or multimer . No invertase activity was detected in suc2 probably a dimer or multimer . No invertase activity was detected in suc2 mutants,--The SNF1 locus is not tightly linked to SUC2 . The snf1 mutations were found to be pleiotropic, preventing sucrose utilization by SUC2+ and SUC7+ strains, and also preventing utilization of galactose, maltose and several nonfermentable carbon sources . Although snf1 mutants thus display a petite phenotype, classic petite mutations do not interfere with utilization of sucrose, galactose or maltose . A common feature of all the carbon utilization systems affected by SNF1 is that all are regulated by glucose repression . The snf1 mutants were found to produce the constitutive nonglycosylated form of invertase, but failed to produce the glucose-repressible, glycosylated, secreted invertase . This failure cannot be attributed to a general defect in production of glycosylated and secreted proteins because synthesis of acid phosphatase, a glycosylated secreted protein not subject to glucose repression, was not affected by snf1 mutations . These findings suggest that the SNF1 locus is involved in the regulation of gene expression by glucose repression.

Mutat Res, 1981 Apr, 81(2), 155 - 64
An unexpected response to Torulopsis glabrata fusion products to X-irradiation; Galeotti CL et al.; Intra-species fusion products of Saccharomyces cerevisiae, Saccharomyces unisporus and Torulopsis glabrata have been isolated following polyethylene glycol-induced fusion of protoplasts and selection for prototrophic colonies . Staining with lomofungin showed that all fusion products were uninucleate . Measurement of DNA content mostly gave values between haploid and diploid levels indicating that the majority of fusion products were aneuploid, Nevertheless fusion products of S . cerevisiae and S . unisporus were, as expected, more resistant to X-irradiation than their haploid parents . By contrast, the X-ray dose-response curve of all T . glabrata fusion products was indistinguishable from their progenitors despite the fact that mitotic segregants could be recovered amongst the survivors to X-rays . A possible explanation for the behaviour towards X-rays of T . glabrata fusion products is that this species lacks a DNA repair pathway involving recombination between homologous chromosomes . We conclude from this study that the shape of the X-ray dose-response curve should not be taken to indicate the ploidy of new yeast isolates without supporting data.

Appl Environ Microbiol, 1981 Apr, 41(4), 992 - 9
Mutants of Saccharomyces cerevisiae and Candida utilis with increased susceptibility to digestive enzymes; Mehta RD et al.; Mutants of Candida utilis and a haploid strain of Saccharomyces cerevisiae were isolated, after ultraviolet light mutagenesis, which had increased sensitivities to snail gut enzymes (ses) . Three of the five S . cerevisiae mutants tested had increased sensitivities to porcine pepsin, all were more susceptible to a sequential treatment with pepsin, lipase, peptidase, and trypsin, four were sensitive to osmotic shock, and two had increased glucan/mannan ratios in their cell walls . All combinations of mutants showed positive complementation in heterozygous diploids, although complementation between one pair, which had the same phenotype, was incomplete, indicating that four to five different cistrons were involved . All mutations were found to be recessive . Haploid strains bearing pairs of ses mutations were not markedly more sensitive to mammalian digestive enzymes than strains with single mutations . Rat-feeding experiments with three mutants and the parental strains indicated that the protein was efficiently utilized in all cases . Net protein ratios for the two mutants of S . cerevisiae tested were slightly higher than that for their parent, but the differences were of marginal significance.

Proc Natl Acad Sci U S A, 1981 Apr, 78(4), 2199 - 203
Fusion of Escherichia coli lacZ to the cytochrome c gene of Saccharomyces cerevisiae; Guarente L et al.; Hybrid genes between the Escherichia coli lacZ gene and the iso-1-cytochrome c (CYC1) gene of Saccharomyces cerevisiae were constructed by recombination in vitro . Each of the hybrid genes encodes a chimeric protein with a cytochrome c moiety at the amino terminus and an active beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) moiety at the carboxy terminus . When these hybrids are introduced into S . cerevisiae on plasmid vectors, they direct synthesis of beta-galactosidase . beta-Galactosidase levels directed by one such plasmid display the pattern of regulation normally seen for cytochrome c (i.e., a reduction of synthesis in cells grown in glucose) . This plasmid contains one codon of CYC1 fused to lacZ, and the fused gene is preceded by the 1100 nucleotides that lie upstream from CYC1 . An analysis of deletions in the upstream DNA suggests that sequences required for efficient transcription initiation of CYC1 lie within the DNA segment 250--700 base pairs upstream from the start of the CYC1 coding sequence . This region is at least 130 base pairs upstream from the "Hogness box" sequence that precedes the CYC1 coding sequence.

J Biochem (Tokyo), 1981 Feb, 89(2), 523 - 9
Saturated fatty acid-starved cells of Saccharomyces cerevisiae grown in the presence of cerulenin and oleic acid; Otoguro K et al.; Cell growth of Saccharomyces cerevisiae ATCC 12341 inhibited by the antibiotic cerulenin, a specific inhibitor of fatty acid synthesis, was restored by oleic acid (18 : 1) to give saturated fatty acid-starved cells, which could not grow when again transferred into a fresh synthetic medium containing the antibiotic and oleic acid . The growth of the saturated fatty acid-starved cells was restored when they were transferred into a medium supplemented with myristic acid (14 : 0), pentadecanoic acid (15 : 0), and palmitic acid (16 : 0) in the presence of cerulenin and oleic acid . Cellular saturated fatty acid content in the growth-restored cells was also restored to about two-thirds of that of the normal yeast cells . The DNA, RNA, and cell wall synthetic capabilities of the saturated fatty acid-starved cells were almost normal, but the L-leucine uptake and cytochrome pattern were severely impaired . These impairments were reversed on supplying palmitic acid . The decrease of L-leucine uptake of the yeasts was also caused by the addition of cerulenin alone . However, since the decrease occurred later than the inhibition of fatty acid synthesis, it was considered to be a secondary effect . These results, obtained by using the saturated fatty acid-starved cells, indicate that the membranes of S . cerevisiae require certain amounts of saturated fatty acid and that the membrane functions (energy metabolism, transport, and so on) are impaired by starvation of saturated fatty acids.

Int J Pept Protein Res, 1981 Feb, 17(2), 219 - 30
Synthesis of the dodecapeptide-alpha mating factor of Saccharomyces cerevisiae; Khan SA et al.; The synthesis of His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr, the dodecapeptide alpha-mating factor from Saccharomyces cerevisiae, and its Ala2- and Cha2-(beta-cyclohexylalanine) analogs are reported . Peptides were synthesized in solution using a combination of mixed anhydride and 1-hydroxybenzotriazole accelerated active ester coupling procedures . Dilute methanesulfonic acid (0.1-0.2 M) in methylene chloride-formic acid solution was employed to specifically remove the tert.-butoxycarbonyl group in the presence of the benzyloxycarbonyl group . Free peptides were obtained using catalytic transfer hydrogenation with formic acid as the hydrogen donor followed by mild acidolysis with trifluoroacetic acid . The alpha-factor and the Cha2-analog exhibited almost equal ability to cause "shmooing" of a-mating types of S . cerevisiae whereas the Ala2-analog exhibited no activity in this assay . These results differ with structure-activity studies reported on the tridecapeptide alpha-factor.

J Gen Microbiol, 1981 Jan, 122(Pt 1), 101 - 7
Growth characteristics of Saccharomyces cerevisiae and Aspergillus nidulans when biotin is replaced by aspartic and fatty acids; Adler JH et al.; When either aerobic or anaerobic cultures of Saccharomyces cerevisiae were supplemented with aspartic and fatty acids in place of biotin, stationary phase populations were very small compared with those obtained in the presence of biotin . Similarly, these acids failed to fulfil the role of biotin-requiring strain of Aspergillus nidulans . Furthermore, a requirement for saturated fatty acid was found with anaerobically cultured S . cerevisiae . Cells were fragmented when biotin was replaced by aspartic and oleic acids alone, while cellular integrity was maintained, but with only slight growth, when biotin was replaced by oleic and palmitic acids together with aspartate . The importance of biotin in the growth of A . nidulans was particularly pronounced in the presence of glucose . In a medium containing glucose, growth ceased when biotin was replaced by aspartate and Tween 80 (a source of saturated and unsaturated fatty acids), but such replacement permitted a very small amount of growth to occur in the absence of glucose.

Mol Gen Genet, 1981, 182(1), 65 - 9
The two methionine adenosyl transferases in Saccharomyces cerevisiae: evidence for the existence of dimeric enzymes; Cherest H et al.; In Saccharomyces cerevisiae either of the two genes SAM1 and SAM2 is able to produce a functional methionine adenosyl transferase (MATI and MATII) . In a wild-type strain, MATI and MATII are present in dimeric forms: MATI-MATI, MATII-MATII and perhaps MATI-MATII . A hypothesis is presented to explain the possible role of these different forms of methionine adenosyl transferase in S . cerevisiae.

Ann N Y Acad Sci, 1981, 369, 321 - 34
Electrochemical measurements of cell populations; Sakato K et al.; Determination of cell growth was carried out by a polarographic system . The system was constructed of two platinum electrodes, a saturated calomel electrode, and a thermistor electrode . Responses of the system to the dissolved oxygen, pH, and temperature were examined . Cell growth of S . cerevisiae and M . olivoasterospora was monitored continuously by this system . In addition, this polarographic system could be applied to the measurements of cell populations of the human cancer cell L-1210 and mouse leukocytes . The measureable range for these animal cells was approximately 10(3)--10(5) cells/ml.

Mutat Res, 1981 Jan, 80(1), 65 - 74
Extreme chemical mutagen sensitivity of respiratory adaptation in yeast; Pasupathy K et al.; The respiratory adaptation process (i.e . essentially mitochondrial biogenesis) in the cells of both wild-type Saccharomyces cerevisiae and strains sensitive to ultraviolet radiation (UV) undergoing transition from the anaerobic to the aerobic state (1-2 h aeration) could be arrested by a prior incubation for 15--30 min with several chemical mutagens and other DNA-acting chemicals at very low concentrations (10-7 to 10-6 M added to cells suspended at the density of 10(7) cells/ml) . At the same concentrations, these chemicals also inhibited DNA and RNA biosynthesis in maturing mitochondria during respiratory adaptation . This provides suggestive evidence for the view that the inhibitory effect of the chemical mutagens on respiratory adaptation could be due to lesions introduced into the DNA of promitochondria in the anaerobic cells . The system of respiratory adaptation in S . cerevisiae cells could serve as a rapid test for ascertaining the potentiality of a chemical to affect cellular DNA and probably, in turn, its potentiality to be mutagenic.

Mol Gen Genet, 1981, 184(3), 394 - 9
Cloning of a eukaryotic regulatory gene; Losson R et al.; From a pool of hybrid plasmids carrying Sau3A fragments representing the entire yeast (S . cerevisiae) genome, a DNA fragment containing the regulatory gene PPRI was cloned by complementation of a non-inducible ppr1 mutation which confers to the cells an increased sensitivity to 6-azauracil . Cells containing the cloned DNA regained the ability to induce the synthesis of URA1 and URA3 gene products controlled by PPR1 . A physical map has been constructed and the study of subcloned restriction endonuclease fragments from the original yeast DNA fragment allowed us to localize the wile-type PPR1 regulatory gene within a 3 kilobase-pair region . The ppr1 RNA level was measured and the hybridization data indicate in a wild-type strain a low efficiency of transcription of PPR1 as compared to the structural URA3 gene, without effect of inducing conditions.

Mol Gen Genet, 1981, 184(3), 386 - 93
Expression of the Herpes simplex virus thymidine kinase gene in Saccharomyces cerevisiae; McNeil JB et al.; Yeast plasmids have been constructed that carry the Herpes simplex Virus type 1 (HSV-1) thymidine kinase (TK) gene which is functionally expressed in Saccharomyces cerevisiae . The expression of the TK gene appears to be due to transcriptional read-through from a yeast promoter that lies on the 3' side of the HIS3 gene . The TK+ yeast possesses in vitro thymidine kinase activity which is absent in the original yeast strain . Yeast strains auxotrophic for thymidine monophosphate (dTMP) (tmp1) can grown on thymidine-containing medium after transformation with these plasmids . Tmp+, TK+ S . cerevisiae whose de novo synthesis of dTMP is inhibited with amethopterin plus sufanilamide is also capable of growth in thymidine . S . cerevisiae transformed with such plasmids is capable of incorporating thymidine and bromodeoxyuridine into DNA.

Nucleic Acids Res, 1980 Dec 11, 8(23), 5725 - 37
Yeast histone mRNA is polyadenylated; Fahrner K et al.; Histone mRNA from S . cerevisiae has been identified and partially purified . The RNA is quantitatively retained on oligo (dT) cellulose or poly(U) sepharose as assayed by in vitro translation or hybridization of radiolabelled cloned yeast histone sequences to RNA immobilized on DBM paper . Retention of yeast histone mRNA on either of these chromatographic systems is most likely the result of polyadenylation since, when primed with oligo (dT), the RNA is an extremely good template for reverse transcriptase, as determined by hybrid arrest translation or by hybridization to D . melanogaster histone DNA sequences.

Genetics, 1980 Dec, 96(4), 841 - 57
The effects of three PSO genes on induced mutagenesis : a novel class of mutationally defective yeast; Cassier C et al.; Reverse and forward mutation, induced by photoaddition of 8-methoxypsoralen (8-MOP) and 3-carbethoxypsoralen (3-CPs) or ultraviolet light (UV), are reduced in three pso mutants of Saccharomyces cerevisiae . The pso1-1 strain exhibits a lower frequency of spontaneous reversion (anti-mutator) and is almost entirely unaffected by the three agents in both the haploid and diploid states . The pso2-1 strain demonstrates very reduced frequencies of 8-MOP and 3-CPs plus 365 nm radiation-induced mutations in haploid and diploid cells . UV-induced mutation are slightly reduced, whereas survival is almost normal . The pso3-1 strain is mutable by 8-MOP and 3-CPs photoaddition only in the low-dose range . After UV treatment, survival of pso3-1 is nearly normal, whereas the frequencies of induced mutants are diminished as compared to the normal PSO+ . An analogue of adenine, 6-N-hydroxyaminopurine, is capable of inducing reversions in wild type, as well as in pso and rad6-1 mutant strains, indicating that this drug may act as a direct mutagen in yeast . The comparison of photoaddition of the bifunctional agent (8-MOP) to that of the monofunctional one (3-CPs) confirms that cross-links, as well as monoadditions, are mutagenic in S . cerevisiae . Repair, of the recombinational type, taking place in diploid cells or in haploid cells in G2 phase leads to higher survival, but appears to be error-free.

Mutat Res, 1980 Dec, 73(2), 251 - 65
Genetic control of diploid recovery after gamma-irradiation in the yeast Saccharomyces cerevisiae; Saeki T et al.; Genetic mechanisms(s) of gamma-ray resistance of the diploid and budding haploid cells of S . cerevisiae were investigated, with special reference to mitotic recombination, by examining 11 rad mutant strains . The radiosensitivity of the diploid was markedly enhanced in certain gamma-ray-sensitive rad mutants, whereas the sensitivity of the haploid was not so enhanced in these rad mutants . These enhanced sensitivities of diploids were irrespective of their own haploid sensitivities . From these results, the existence of a mechanism of diploid-specific recovery was postulated . The magnitude of diploid radioresistance in rad mutants was positively correlated with the ability for the induction of mitotic recombinational events which were controlled by RAD genes belonging to the RAD-51 genetic pathway . The genetic mechanism(s) of the diploid recovery after gamma-irradiation are probably related to recombinational processes between the homologous chromosomes leading to reciprocal recombination or non-reciprocal gene conversion . Furthermore, the higher radioresistance of budding cells in comparison with the non-budding cells was also correlated to the diploid radioresistance with a few exceptions . Consequently, the mechanism(s) of budding radioresistance similar to the diploid recovery seems to be related to mitotic recombinational processes.

Genetics, 1980 Nov, 96(3), 589 - 611
Recombination and chromosome segregation during the single division meiosis in SPO12-1 and SPO13-1 diploids; Klapholz S et al.; This paper reports a study of chromosome segregation and recombination during sporulation of spo12-1 and spo13-1 diploid strains of S . cerevisiae . These strains undergo a single division to form asci containing two diploid or near-diploid spores . The segregation of centromere-linked markers in the two-spored (dyad) products indicates that the division is generally equational . However, in a small percentage of the spo12-1 and spo13-1 cells, it appears that a meiosis I-like division occurs . Aberrant segregation of the MAT locus on chromosome III, yielding a monosomic and a trisomic spores pair, occurs in 12% of all dyads . The segregation patterns of markers at various distances from their centromeres and several pairs of markers on the same chromosome indicate that recombination takes place in both strains at nearly standard meiotic levels.

Genetics, 1980 Nov, 96(3), 567 - 88
Isolation of SPO12-1 and SPO13-1 from a natural variant of yeast that undergoes a single meiotic division; Klapholz S et al.; ATCC4117 is a strain of S . cerevisiae that undergoes a single nuclear division during sporulation to produce asci containing two diploid ascopores (Grewal and Miller 1972) . All clones derived from these spores are sporulation-capable and, like the parental strain, form two-spored asci . In this paper, we describe the genetic analysis of ATCC4117 . In tetraploid hybrids of vegetative cells of the ATCC4117 diploid and a/a or alpha/alpha diploids, the production of two-spored asci is recessive . From these tetraploids, we have isolated two recessive alleles, designated spo12-1 and spo13-1, each of which alone results in the production of asci with two diploid or near-diploid spores . These alleles are unlinked and segregate as single nuclear genes . spo12-1 is approximately 22 cM from its centromere; spo13-1 has been localized to within 1 cM of arg4 on chromosome VIII . This analysis also revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation.

Arch Intern Med . 1980 Nov;140(11):1539.
Saccharomyces cerevisiae septicemia; Eschete ML et al.; We report the first known case of septicemia caused by Saccharomyces cerevisiae . It occurred nosocomially in a hyperalimented burned man . It is a rare example of disease caused by S cerevisiae, which, like many saprophytes, can become pathogenic in the debilitated . The case is remarkable for its apparent origin in a bleeding esophageal lesion, for its clinical characteristics, including profound neutropenia, thrombocytopenia, hypothermia, and monocytopenia, and for its cure by amphotericin B.

Cell, 1980 Nov, 22(2 Pt 2), 427 - 36
Mating signals control expression of mutations resulting from insertion of a transposable repetitive element adjacent to diverse yeast genes; Errede B et al.; ROAM mutations cause overproduction in S . cerevisiae . Overproduction of ROAM mutant gene products is less in MATa/MAT alpha diploid strains which cannot conjugate than in haplolid strains which can . Overproduction occurs in diploid strains capable of mating whether or not they are capable of sporulating . Overproduction decreases when haploid ROAM mutants also contain the ste7 mutation which prevents conjugation; other ste mutations do not affect the expression of ROAM mutations . Cloning of the ROAM mutant gene CYC7-H2 shows that a 5.5 kb sequence homologous to a transposable and reiterated Ty1 element is inserted in the 5' noncoding region of the CYC7 structural locus . The similar genetic properties of other ROAM mutations suggest that they each contain an inserted Ty element . These results also suggest that ROAM mutations respond to signals normally directed toward genes controlling conjugation functions, and that sequences present in Ty elements may be adjacent to structural loci and are the normal receptors for these signals.

J Biol Chem, 1980 Oct 25, 255(20), 9828 - 37
Assembly of the mitochondrial membrane system . DNA sequence and organization of the cytochrome b gene in Saccharomyces cerevisiae D273-10B; Nobrega FG et al.; The mitochondrial genomes of cytoplasmic "petite" (rho-) mutants of Saccharomyces cerevisiae have been used to sequence the cytochrome b gene . A continuous sequence of 6.2 kilobase pairs has been obtained from 71.4 to 80.2 units of the wild type map . This region contains all the cytochrome b mutations previously assigned to the cob1 and cob2 genetic loci . Analysis of the DNA sequence has revealed that in the strain D273-10B, the cytochrome b gene is composed of three exons . The longest exon (b1) codes for the first 252 to 253 amino acids from the NH2-terminal end of the protein . The next two exons (b2 and b3) code for 16 to 18 and 115 to 116 amino acids, respectively . The complete cytochrome b polypeptide chain consists of 385 amino acids . Based on the amino acid composition, the yeast protein has a molecular weight of 44,000 . The three exon regions of the cytochrome b gene are separated by two introns . The intron between b1 and b2 is 1414 nucleotides long and contains a reading frame that is continuous with the reading frame of exon b1 . This intron sequence is potentially capable of coding for another protein of 384 amino acid residues . The second intron is 733 nucleotides long . This sequence is rich in A + T and includes a G + C cluster that may be involved in processing of the cytochrome b messenger . The organization of the cytochrome b region in S . cerevisiae D273-10B is somewhat less complex than has been reported for other yeast strains i which exon b1 appears to be further fragmented into three smaller exons.

Eur J Biochem, 1980 Oct, 111(1), 17 - 31
A flavin-mononucleotide-binding site in Hansenula anomala nicked flavocytochrome b2, requiring the association of two domains; Gervais M et al.; Previous experiments in our laboratory with Saccharomyces cervisiae flavocytochrom b2 indicated that both fragments alpha and beta of the enzyme after cleavage by yeast proteases are required to form the flavin site . More detailed experiments have not been carried out on the nicked Hansenula anomala enzyme obtained by tryptic cleavage . A method has been devised that gives a quantitative separation in 4 M urea of beta, and alpha with its heme still bound . The characteristics of the various species: isolated alpha and beta and mixed alpha + beta were studied in 4 M urea and after elimination of this reagent by dialysis in the presence of FMN and 2-mercaptoethanol . Several methods, including heme spectroscopy, tryptophan fluorescence, sedimentation studies, and titration of bound flavin, were used . The results indicate that isolated alpha and beta have a folded globular structure after renaturation . The flavin binding to the alpha + beta mixture was important (50-100%) with recovery of the flavodehydrogenase activity . In contrast, binding was not detectable (< 0.5%, Kf > 10 mM) for isolated alpha and beta . As far as mononucleotide binding is concerned, such a cooperative requirement for two folding domains has never been reported in other enzymes . The present results are discussed together with others obtained in our laboratory which demonstrate that, as deduced from their sensitivity to trypsin, the structure of S . cerevisiae and H . anomala flavocytochrome b2 protomers is triglobular 'n-x-beta' (n and x combined within alpha) . The tetramer assembly, which remains intact as a nicked enzyme (alpha beta)4 after the first trypsin cleavage, is broken down following a second cleavage of the chain into four cytochrome cores (n) and a functional T-flavodehydrogenase entity, a tetramer of the type (x beta)4.

Antimicrob Agents Chemother, 1980 Oct, 18(4), 593 - 7
Influence of extracellular K+ or Mg2+ on the stages of the antifungal effects of amphotericin B and filipin; Brajtburg J et al.; The macrolide heptaene amphotericin B (AmB) induced concentration-dependent effects on Saccharomyces cerevisiae which were separable into two distinct stages . At low concentrations the drug inhibited the growth of the yeast and reversible changed cell permeability to Na+ and K+ . At high levels it was lethal . The intracellular K+ concentration of cells with reversible damage (stage I) could be increased by addition of K+ to the medium, but cells irreversibly damaged (stage II) were not able to retain K+ . The addition of K+ to the medium did not influence the growth-inhibitory or killing action of AmB . Addition of Mg2+ to cultures increased S . cerevisiae resistance to the killing effects of AmB . At low concentrations of AmB, growth inhibition was also decreased by extracellular Mg2+, but at higher concentration of AmB, growth inhibition was increased, probably because the prevention by Mg2+ of the lethal effect allowed expression of the inhibitory effect in a greater range . Simultaneous addition of K+ and Mg2+ markedly decreased both the inhibitory and lethal action of AmB at all concentrations . Filipin, a pentaene macrolide, had only lethal effects, which were unaffected when K+ was added to the medium but were diminished when medium was supplemented with Mg2+.

Boll Soc Ital Biol Sper, 1980 Sep 30, 56(18), 1803 - 6
Genetic effects of vinylcyclohexene diepoxide in yeast; Bronzetti G et al.; Using D7 strain of S . cerevisiae where we can consider three genetic effects such as mitotic gene conversion, mitotic cross over and reverse mutation we tested vinylcyclohexene diepoxide "in vitro" without metabolic activation . In this condition VCD is very toxic and induces both three genetic effects namely mitotic gene conversion, mitotic cross over and reverse mutation.

J Bacteriol, 1980 Sep, 143(3), 1411 - 9
Changes in regulation of ribosomal protein synthesis during vegetative growth and sporulation of Saccharomyces cerevisiae; Pearson NJ et al.; When diploid Saccharomyces cerevisiae cells logarithmically growing in acetate medium were placed in sporulation medium, the relative rates of synthesis of 40 or more individual ribosomal proteins (r-proteins) were coordinately depressed to approximately 20% of those of growing cells . These new depressed rates remained constant for at least 10 h into sporulation . If yeast nitrogen base was added 4 yh after the beginning of sporulation to shift the cells back to vegetative growth, the original relative rates of r-protein synthesis were rapidly reestablished . this upshift in the rates occurred even in diploids homozygous for the regulatory mutation rna2 at the restrictive temperature for this mutation (34 degrees C) . However, once these mutant cells began to bud and grow at 34 degrees C, the phenotype of rna2 was expressed and the syntheses of r-proteins were again coordinately depressed . At least one protein whose rate of synthesis was not depressed by rna2 in vegetative cells did have a decreased rate of synthesis during sporulation . Another r-protein whose synthesis was depressed by rna2 maintained a high rate of synthesis at the beginning of sporulation . These data suggest that the mechanism responsible for coordinate control of r-protein synthesis during sporulation does not require the gene product of RNA2 and thus defines a separate mechanism by which r-proteins are coordinately controlled in S . cerevisiae.

Eur J Biochem, 1980 Sep, 110(1), 107 - 14
Structure of the 5-S ribosomal RNA gene and its adjacent regions in Torulopsis utilis; Tabata S; A DNA segment spanning one repeating unit of ribosomal RNA(rRNA) genes in a yeast strain, Torulopsis utilis, has been cloned on a bacterial plasmid pBR322 . The size of the cloned segment was about Mr = 8.0 x 10(6) . All of the genes for the four species of rRNA were linked on it, and there was a long spacer between the 5-S and 18-S rRNA coding regions . The nucleotide sequences of the regions flanking the 5-S rRNA gene were determined and compared with those in the corresponding regions of Sacharomyces cerevisiae {Valenzuela, P., Bell, G . I., Masiarz, F . R., DeGennaro, L . J., and Rutter, W . J . (1977) Nature, 267, 641-643; Maxam A . M., Tizard, R., Skryabin, K . G., and Gilbert, W . (1977) Nature, 267, 643-645} . The sequence of the T . utilis 5-S rRNA is identical with that of S . cerevisiae except for two residues at positions 18 and 61 . However, its upstream region contained a quite different sequence, and a sequence which showed some homology was only found at positions -21 to -28 . The sequences were d(T-G-T-A-A-C-C-T) in T . utilis and d(T-A-T-C-A-C-C-T) in S . cerevisiae . Although the presence of various repeat sequences having the same or opposite directions was noted, these repeats occurred at different positions in the two yeast species . In the downstream region, the common sequence was only seven dT deoxynucleotides, which occurred immediately after the 5-S rRNA coding sequence . Significant direct and inverted repeat sequences were found in T . utilis, but such repeats are not seen in S . cerevisiae.

J Bacteriol, 1980 Aug, 143(2), 621 - 7
Synthesis of beta-glucanases during sporulation in Saccharomyces cerevisiae: formation of a new, sporulation-specific 1,3-beta-glucanase; del Rey F et al.; A biphasic synthesis of 1,3-beta-glucanase occurred when cells of Saccharomyces cerevisiae AP-1 (a/alpha) were incubated in sporulation medium . The capacity to degrade laminarin increased very slowly during the first 7 h but at a much faster rate thereafter . Changes occurring during the first period were not sporulation specific since the moderate increase in activity against laminarin was insensitive to glutamine and hydroxyurea and also took place in the nonsporulating strain S . cerevisiae AP-1 (alpha/alpha) . However, the changes taking place after 7 h must be included in the group of sporulation-specific events since they were inhibited by glucose, glutamine, and hydroxyurea and did not occur in the nonsporulating diploid . Consequently, only when the cells had been incubated for at least 7 h in sporulation medium did full induction of activity against laminarin take place upon shift to a medium which favored vegetative growth . Changes in the relative proportions of the vegetative glucanases, namely, endo- and exo-1,3-beta-glucanase, and the formation of a new sporulation-specific 1,3-beta-glucanase account for the observed events and are the consequence of the expression of the sporulation program.

J Bacteriol, 1980 Aug, 143(2), 1066 - 9
Separation of peptide transport and hydrolysis in trimethionine uptake by Saccharomyces cerevisiae; Parker DD et al.; Intact cells of Saccharomyces cerevisiae 139 hydrolyzed amino acid-p-nitroanilide by an activity similar to that of aminopeptidase II, as well-characterized external peptidase in yeast . In contrast, trimethionine, a model peptide used in transport assays, was not hydrolyzed by this aminopeptidase II-like activity, and the peptidase activity toward this substrate was localized in the soluble fraction of the yeast . We conclude that this tripeptide is taken up by S . cerevisiae intact and rapidly hydrolyzed inside the cell.

Gut, 1980 Aug, 21(8), 643 - 9
Defective opsonisation and complement deficiency in serum from patients with fulminant hepatic failure; Wyke RJ et al.; Serum from 23 of 26 patients with fulminant hepatic failure and grade IV encephalopathy had defective opsonisation of E . coli and yeast (S . cerevisiae) . No toxic serum factors acting on the polymorphonuclear leucocytes or inactivators of the normal serum opsonisation factors were found . Complement deficiency was shown to be the most likely cause of the defect in opsonisation . The addition of a heat-labile fraction of normal serum at low concentration corrected the defect and factors of both the classical and the alternative pathways of complement were reduced to below 40% of the activity of the control serum . During the early stages of clinical recovery serum opsonisation and complement activity returned to normal with statistically significant correlations between tests of opsonisation and total haemolytic complement CH50, C3 and total alternative pathway activity . Defective serum opsonisation and complement deficiency represent major defects in the body's defences against infection.

Proc Natl Acad Sci U S A, 1980 Aug, 77(8), 4559 - 63
Eukaryotic DNA segments capable of autonomous replication in yeast; Stinchcomb DT et al.; A selective scheme is presented for isolating sequences capable of replicating autonomously in the yeast Saccharomyces cerevisiae . YIp5, a vector that contains the yeast gene ura3, does not transform a ura3 deletion mutant to Ura+ . Hybrid YIp5-Escherichia coli DNA molecules also fail to produce transformants . However, collections of molecular hybrids between YIp5 and DNA from any of six eukaryotes tested (S . cerevisiae, Neurospora crassa, Dictyostelium discoideum Ceanhorabditis elegans, Drosophila melanogaster, and Zea mays) do transform the deletion mutant . The Ura+ transformants grow slowly, are unstable under nonselective conditions, and carry the transforming DNA as autonomously replicating, supercoiled circular molecules . Such a phenotype is qualitatively identical to that of strains transformed by molecules containing a yeast chromosomal origin of replication . Thus, these DNA hybrid molecules may contain eukaryotic origins of replication . The isolated sequences may be useful in determiing the signals controlling DNA replication in yeast and in studying both DNA replication and transformation in other eukaryotic organisms.

Antimicrob Agents Chemother, 1980 Aug, 18(2), 226 - 30
Classification of polyene antibiotics according to their synergistic effect in combination with bleomycin A2 or fusidic acid; Akiyama S et al.; Five polyene antibiotics were compared for their effects on colony formation of either Chinese hamster V79 or Saccharomyces cerevisiae cells . A 10 to 40 times higher concentration of amphotericin B (heptaene) or nystatin (degenerated heptaene) was necessary to inhibit colony formation of hamster cells than that needed to inhibit colony formation of yeast cells . In contrast, colony formation of both hamster and yeast cells was inhibited to the same extent by similar concentrations of filipin (pentaene), pentamycin (pentaene), or pimaricin (tetraene) . The five polyene antibiotics were also compared for their effects on colony formation of either V79 or S . cerevisiae cells when combined with a nonpolyene antibiotic, fusidic acid or bleomycin A2 . Amphotericin B or nystatin could augment the cytocidal effect of fusidic acid but not that of bleomycin A2, whereas pentamycin or pimaricin could augment the cytocidal effect of both fusidic acid and bleomycin A2 against hamster and yeast cells . Filipin was found to enhance the action of fusidic acid and bleomycin upon growth of mammalian cells, whereas the pentaene polyene significantly potentiated the action of fusidic acid, but not that of bleomycin A2, against S . cerevisiae . It was therefore suggested that these polyene antibiotics be classified into two groups: group 1 (pimaricin, pentamycin, and filipin) and group 2 (amphotericin B and nystatin).

Genetics, 1980 Jul, 95(3), 579 - 88
The selection of amber mutations in genes required for completion of start, the controlling event of the cell division cycle of S . cerevisiae; Reed SI; Using a modification of a procedure developed for the isolation of temperature-sensitive mutants defective in the start event of cell division, amber mutations were obtained for two Class-I start genes, cdc28 and cdc37 . Genetic analysis demonstrated that co-segregation of an amber suppressor with such alleles was required for viability of spores subsequent to meiosis . These mutations are expected to be useful in the identification of the molecular products of the genes cdc28 and cdc37.

Genetics, 1980 Jul, 95(3), 561 - 77
The selection of S . cerevisiae mutants defective in the start event of cell division; Reed SI; Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization . Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously . Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another . One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division . After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

J Bacteriol, 1980 Jul, 143(1), 176 - 81
Choline transport in Saccharomyces cerevisiae; Hosaka K et al.; Choline transport of Saccharomyces cerevisiae was measured by the filtration method with the use of glass microfiber paper . The uptake was time and temperature dependent . The kinetics of choline transport showed Michaelis behavior; an appearent Km for choline was 0.56 microM . N-Methylethanolamine, N,N-dimethylethanolamine, and beta-methylcholine were competitive inhibitors of choline transport, with Ki values of 40.1, 3.1, and 6.9 microM, respectively . Ethanolamine, phosphorylcholine, and various amino acids examined had no effect . Choline transport required metabolic energy; removal of glucose resulted in a great loss of transport activity, and the remaining activity was abolished by 2,4-dinitrophenol, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, arsenate, and cyanide . External Na+ was not required, and the transport was not effected by ionophores, valinomycin, and gramicidin D . These results indicate that S . cerevisiae possess an active choline transport system mediated by a specific carrier . This view is further supported by the isolation and characterization of a choline transport mutant . The choline transport activity in this mutant was very low, whereas the transport of L-leucine, L-methionine, D-glucose, and myo-inositol was normal . Together with the choline transport mutant, mutants defective in choline kinase were also isolated.

Boll Soc Ital Biol Sper, 1980 Jun 30, 56(12), 1315 - 21
{Use of the D7 strain of S . cerevisiae in the determination of environmental risk . 1 . Genetic effects of trichloroethylene}; Bronzetti G et al.; Trichloroethylene (TCE) was tested for its ability to induce both point mutation and mitotic gene conversion in diploid strain of yeast . S . cerevisiae (strain D7) was tested for both activities in culture with and without a mammalian microsomal activation system and intrasanguinous host-mediated assay in mice . In suspension test with D7, TCE was genetically active only with microsomal activation . In vivo TCE induced both point mutation and gene conversion in D7 and gene conversion in D4 when recovered from the liver and kidneys after both acute and subacute dosing . Yeasts recovered from the lungs showed little, if any, increase in genetic effects.

Mutat Res, 1980 Jun, 71(1), 77 - 89
Yeast mitochondrial deoxyribonuclease stimulated by ethidium bromide . III . Possible invovlement in the induction of "petite" mutation by phenanthridinium derivatives; Jacquemin-Sablon H et al.; We previously described a yeast-mitochondrial deoxyribonuclease (EtdBr DNAase), whose activity is stimulated by ethidium bromide . In this paper, we have compared the ability of a series of phenanthridinium derivatives to activate the EtdBr DNAase "in vitro" and their efficiency in inducing "petite" mutants in the yeast S . cerevisiae . Kinetics studies, in the absence or the presence of SDS, were first carried out to compare the penetration rates of the various compounds . Dose--response curves were then established to quantify their mutagenic efficiencies . From these data, a linear correlation was established between the level of EtdBr DNAase activation produced by a drug and its mutagenic efficiency, thus demonstrating that the two processes display similar drug-structural requirements . These results suggest that the EtdBr DNAase might be involved in the induction of petite mutations by these derivatives.

Eur J Biochem, 1980 Jun, 107(2), 501 - 4
Direct oxidation of NADPH by submitochondrial particles from Saccharomyces cerevisiae; Djavadi FH et al.; It has been accepted that in Saccharomyces cerevisiae submitochondrial particles do not oxidize the NADPH and that the NADPH:cytochrome c reductase is not a mitochondrial enzyme but rather a microsomal one . The present study provides clear evidence that in S . cerevisiae a direct oxidation of NADPH occurs through the mitochondrial electron transport system . The following results wee obtained: submitochondrial particles from S . cerevisiae are capable of oxidizing NADPH with a relatively high rate . The oxidation of NADPH is sensitive to antimycin A and NaN3 but insensitive to rotenone as is known for NADPH oxidation . Also NADPH:cytochrome c reductase activity is inhibited by antimycin A . NADPH-induced reduction of cytochromes b, c + c1, and aa3 is as fast as NADPH-induced reduction . Cytochromes are reduced to the same extent with either NADH or NADPH . The changes of the ratio of NADH/NADPH oxidation rate and the ratio of NADH K3Fe(CN)6/NADPH-K3Fe(CN)6 reductase activities at various phases of growth suggest that two distinct pyridine nucleotide dehydrogenases could be responsible for NADH and NADPH oxidation . This problem remains to be elucidated.

Mutat Res, 1980 Apr, 77(4), 341 - 4
{Effect of smoking-machine parameters on the genetoxic activity of cigarette gas phase, estimated on human lymphocyte and yeast (author's transl)}; Izard C et al.; Cigarette smoke used in chemical research and bioassays is obtained by mechanical smoking on machines adjusted to international standards . On studying the behavior of some smokers of black tobacco, we were led to change the standard parameters: volume, duration, frequency . The gas phase obtained under those new conditions is poorer in some components . This decrease goes with a clear-cut decrease of its genotoxic activity towards cultured human lymphocytes (sister-chromatid exchange frequency) and S . cerevisiae (rate of mitotic recombinants and of respiratory deficients) . This investigation emphasizes the leading part of the smoking behavior.

Biochim Biophys Acta, 1980 Mar 27, 597(1), 125 - 36
Uptake of the lipophilic cation dibenzyldimethylammonium into Saccharomyces cerevisiae . Interaction with the thiamine transport system; Barts PW et al.; The distribution ratio of the lipophilic cation dibenzyldimethylammonium between the cells of Saccharomyces cerevisiae and the medium appears to reflect changes in the membrane potential in a way that is qualitatively correct: the addition of a proton conductor or of an agent which blocks metabolism causes an apparent depolarization of the cell membrane; monovalent cations cause also a lowering of the equilibrium distribution, whereas the addition of divalent cations results in an increase of the partition ratio . However, uptake of dibenzyldimethylammonium and probably also of other liophilic cations proceeds via the thiamine transport system of the yeast . Dibenzyldimethylammonium transport is inducible, like thiamine transport . A kinetic analysis of the mutual interaction between thiamine and dibenzyldimethylammonium uptake shows that these compounds share a common transport system; moreover, dibenzyldimethylammonium uptake is inhibited complete by thiamine disulfide, a competitive inhibitor of thiamine transport and dibenzyldimethylammonium uptake in a thiamine-transport mutant is reduced considerably . It is concluded that one should be cautious when using lipophilic cations to measure the membrane potential of cells of S . cerevisiae.

J Biol Chem, 1980 Mar 25, 255(6), 2569 - 77
Formyl-methenyl-methylenetetrahydrofolate synthetase(combined) from yeast . Biochemical characterization of the protein from an ade3 mutant lacking the formyltetrahydrofolate synthetase function; de Mata ZS et al.; A protein from Saccharomyces cerevisiae mutant ade3-1050, a formyltetrahydrofolate synthetase-deficient mutant, has been purified to apparent homogeneity . The purified mutant enzyme shows both methylenetetrahydrofolate dehydrogenase and methenyltetrahydrofolate cyclohydrolase activities, but lacks formyltetrahydrofolate synthetase activity . The biochemical characterization of the mutant protein described in this paper is consistent with genetic data which indicate that the 1050 mutation is a point mutation at the ade3 locus of chromosome VII of S . cerevisiae . The molecular weight of the native mutant protein (Mr = 227,000 by exclusion chromatography), as well as the number and size of its subunits are exactly the same as those of the trifunctional wild type enzyme . In addition, both proteins have the same sedimentation behavior in a glycerol density gradient (s20,w = 9.4 S), and their activities and structures are equally affected by exposure to mild tryptic degradation . ATP protects both enzymes from tryptic degradation, but NADP+ does not . Some of the kinetic properties of the activities of both enzymes were also determined and were essentially similar . Although both enzymes require the presence of metals for maximal synthetase and dehydrogenase activities, metals are not necessary to maintain their structures intact.

Nucleic Acids Res, 1980 Mar 11, 8(5), 1043 - 59
Molecular cloning of the actin gene from yeast Saccharomyces cerevisiae; Gallwitz D et al.; Two overlapping DNA fragments from yeast Saccharomyces cerevisiae containing the actin gene have been inserted into pBR322 and cloned in E.coli . Clones were identified by hybridization to complementary RNA from a plasmid containing a copy of Dictyostelium actin mRNA . One recombinant plasmid obtained (pYA102) contains a 3.93-kb Hindlll fragment, the other (pYA208) a 5.1-kb Pstl fragment, both share a common 2.2-kb fragment harboring part of the actin gene . Cloned yeast actin DNA was identified by R-loop formation and translation of the hybridized actin mRNA and by DNA sequence analysis . Cytoplasmic actin mRNA has been estimated to be about 1250 nucleotides long . There is only one type of the actin gene in S.cerevisiae.

Nucleic Acids Res, 1980 Mar 11, 8(5), 1009 - 22
Hybridizable sequences between cytoplasmic ribosomal RNAs and 3 micron circular DNAs of Saccharomyces cerevisiae and Torulopsis glabrata; Clark-Walker GD et al.; We have shown that 2.8 and 3.1 micron circular DNA molecules, previously reported to be present in Saccharomyces cerevisiae and Torulopsis glabrata respectively, contain sequences hybridizing to cytoplasmic ribosomal RNAs . In S . cerevisiae the 2.8 micron circular DNA appears to be identical to the rDNA repeating unit from nuclear DNA, both in length (approximately 9000 base pairs) and in the location of the 25, 18 and 5.8S rRNA sequences on the large HindIII fragment (6500 bp) and the presence of the 5S rRNA sequence on the small HindIII fragment . The 3.1 micron molecule from T . glabrata is approximately 2000 base pairs longer than the S . cerevisiae molecule and in addition, one of the HindIII sites lies within the region hybridizing to 25, 18 and 5.8S rRNAs . In S . cerevisiae the 4-5 copies of the 2.8 micron circular DNA molecules per cell, which have an extra-nuclear location, do not appear to be essential for cell viability as in one strain they were undetectable.

Genetics, 1980 Mar, 94(3), 555 - 80
Structural analysis of the dur loci in S . cerevisiae: two domains of a single multifunctional gene; Cooper TG et al.; In Saccharomyces cerevisiae, the degradation of urea to carbon dioxide and ammonia is catalyzed by urea carboxylase and allophanate hydrolase . The loci coding for these enzymes (dur1 and dur2) are very tightly linked on the right arm of chromosome II between pet11 and met8 . Pleiotropic mutations that fail to complement mutations in either of the dur loci were found to be predominantly located in or near the dur2 locus . We interpret these data as suggesting that the two dur loci might in reality be domains of a single gene that codes for a multifunctional polypeptide . In view of this conclusion, we have renamed the dur loci as the dur1,2 locus.

Nucleic Acids Res, 1980 Feb 11, 8(3), 467 - 85
More ribosomal spacer sequences from Xenopus laevis; Moss T et al.; The base sequence analysis of a Xenopus laevis ribosomal DNA repeat (7) has been extended to cover almost the entire non-transcribed and external transcribed spacer . A compilation of these sequences is presented . All the repetitive and non-repetitive sequence elements of the spacer are identified and their evolution discussed . Comparison of the X.laevis and S.cerevisiae (25,26) ribosomal DNAs shows about 80% sequence conservation in the 18S gene but no sequence conservation, from the available data, in the external transcribed spacer . The sequence coding for the 3' terminus of the X.laevis 40S ribosomal precursor RNA is presented and its structural features analyzed.

Cell, 1980 Feb, 19(2), 403 - 14
Translational analysis of the killer-associated virus-like particle dsRNA genome of S . cerevisiae: M dsRNA encodes toxin; Bostian KA et al.; The M species (medium sized) dsRNA (1.1-1.4 x 10(6) daltons) isolated from a toxin-producing yeast killer strain (K+R+) and three related, defective interfering (suppressive) S species dsRNAs of the yeast killer-associated cytoplasmic multicomponent viral-like particle system were analyzed by in vitro translation in a wheat germ cell-free protein synthesis system . Heat-denatured M species dsRNA programmed the synthesis of two major polypeptides, M-P1 (32,000 daltons) and M-P2 (30,000 daltons) . M-P1 has been shown by the criteria of proteolytic peptide mapping and cross-antigenicity to contain ihe 12,000 dalton polypeptide corresponding to the in vivo produced killer toxin, thus establishing thiat it is the M species dsRNA which carries the toxin gene . An M species dsRNA obtained from a neutral strain (K-R+) also programmed the in vitro synthesis of a polypeptide identical in molecular weight to M-P1, thus indicating that the cytoplasmic determinant of the mutant neutral phenotype is either a simple point mutation in the dsRNA toxin gene or a mutation in a dsRNA gene which is required for functional toxin production . In vitro translation of each of the three different suppressive S dsRNAs resulted in the production of a polypeptide (S-P1) of approximately 8000 daltons instead of the 32,000 dalton M-P1 polypeptide programmed by M dsRNA . This result is consistent with the heteroduplex analysis of these dsRNAs by Fried and Fink (1978), which shows retention of M dsRNA ends, accompanied by large internal deletions in each of the S dsRNAs translated.

Z Allg Mikrobiol, 1980, 20(10), 641 - 52
{Cell electrophoretical characterization of the surface of Candida guilliermondii}; Lerche KH et al.; The electrical properties of the outer layer of the cell wall of a hydrocarbon-grown yeast C . guilliermondii were studied in detail by cell electrophoresis . Some experiments were also made with the yeast S . cerevisiae . The mobilities of the yeasts were measured as a function of pH at pH 2-11.5 and constant ionic strength I = 0.02 mol/l . For identification of surface groups the pH-mobility curves are used to calculate pK-values . The results indicate the presence of amino and carboxyl groups on the surface of C . guilliermondii . These groups are probably a part of a glyco-protein with an isoelectric point at pH 3.3 located on the surface . Electrophoresis of droplets of mineral oil coated with adsorbed protein layer confirms these conclusions . The importance of this glycoprotein in hydrocarbon uptake is discussed.

Mol Gen Genet, 1980, 177(4), 581 - 8
Analysis of rho mutability in Saccharomyces cerevisiae . I . Effects of mmc and pet-ts alleles; Marmiroli N et al.; Two additional types of nuclear determinants involved in the control of spontaneous mutability of rho in S . cerevisiae have been identified: mmc and the pet-ts 1, 2, 10, 52 and 53 genes . These genes in their mutated recessive form increase at various extents the number of respiratory deficient cytoplasmic "petite" mutants accumulated . The gene mmc does not affect the respiratory activity and is not temperature-dependent whereas the pet-ts genes determine at the non permissive temperature a respiratory deficient phenotypes even if they affect the mutability of rho at the permissive and at the non permissive temperature . The data here reported suggest that a "replicative complex" exists for the mitochondrial DNA . It is in the purpose of this paper to deal with the relative contribution that mmc and pet-ts gene products have in ensuring the fidelity of this "replicative complex".

Birth Defects Orig Artic Ser, 1980, 16(1), 179 - 93
Towards enzyme replacement in GM2 gangliosidosis: organ disposition and induced central nervous system uptake of human beta-hexosaminidase in the cat; Rattazzi MC et al.; The rapid plasma clearance of human placental beta-hexosaminidase in the cat is due mainly to a receptor-mediated mechanism recognizing terminal N-acetyl glucosaminyl and mannosyl residues on glycoproteins . Using a sensitive single radial immunodiffusion assay, specific for human beta-hexosaminidase, we have shown that, in normal cats, the liver is responsible for most of the clearance of human beta-hexosaminidase . Two hours after injection of approximately 6 X 10(6) U beta-hexosaminidase/kg bw, 70-90% of the enzyme was recovered in the liver . Spleen, kidney, lung, bone, bone, pancreas, adrenals, testes and ovaries, cardiac and skeletal muscle, lymph nodes, and placenta, however, also participated in the clearance, although specific uptake in most organs was < 5% of that of liver . Exogenous beta-hexosaminidase was also present in bile, indicating that the hepatocytes are involved in clearance . Injection of terminal mannose-rich S . cerevisiae mannans (50-150 mg/kg bw), prolonged the plasma half-life of the enzyme (t 1/2 up to 290 min) . In these animals, beta-hexosaminidase uptake by liver was reduced to < 10% of controls but uptake by other organs was not proportionally or uniformly reduced, suggesting the existence of different uptake mechanisms in different tissues . Permeability of the blood-brain barrier was induced by exposing cats to 100% O2 at 2.5 ATA for 90 min . Injection of 6 X 10(6) U beta-hexosaminidase/kg bw during or immediately after exposure resulted in apparent uptake of enzyme by nervous tissue, qualitatively detectable by immunologic methods, but below the limits of sensitivity of the radial immunoassay(ie < 150 U/gr) . When enzyme uptake by liver was inhibited by injection of ovomucoid or mannans, however, the hyperbaric oxygen-induced apparent uptake of beta-hexosaminidase by brain, cerebellum, and spinal cord was 200-500 U/gr of blood-free tissue, suggesting that the transport mechanism involved (presumably at the level of the nervous system vascular endothelium) is different from the carbohydrate-dependent hepatic uptake . The mechanism by which hyperbaric oxygenation induces permeability of the blood-brain barrier is not clear . The combination of this procedure (routinely used in human therapy) with specific inhibition of hepatic uptake, however, appears to be a promising approach for lysosomal enzyme targeting to the central nervous system.

Genetics, 1979 Dec, 93(4), 877 - 901
A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci; Rine J et al.; A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S . cerevisiae . This suppressor, sir1-1, restores mating ability to mat alpha 1 and mat alpha 2 mutants and restores sporulation ability to mat alpha 2 and mata1 mutants . MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to alpha-factor, both properties of a/alpha diploids . Furthermore, sir1-1 allows MATa/MATa, mat alpha 1/mat alpha/, and MAT alpha/MAT alpha strains to sporulate efficiently . All actions of sir1-1 are recessive to SIR1 . The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed . The ability of sir1-1 to suppress the mat alpha 1-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to alpha . Thus, as predicted by the cassette model, HMa is functionally equivalent to MAT alpha since it supplies functions of MAT alpha . We propose that sir1-1 is defective in a function . Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HM alpha.

Tsitologiia, 1979 Dec, 21(12), 1403 - 10
{Cytochemical and biochemical determination of acid phosphatase activity in yeasts}; Rainina EP et al.; Optimal conditions of the cytochemical assay for acid phosphatase in protoplasts and whole cells of S . cerevisiae have been described . Dimethyl sulfoxide was used to increase the permeability of the yeast cell envelope . In the yeast cells, grown up to the end of the exponential phase, acid phosphatase is shown to be located mainly in the central vacuole and on the cell envelope surface . A considerable activity of acid phosphatase is demonstrable on the surface of the plasma membrane and within adjacent vesicles that represent, presumably, part of the endoplasmic reticulum . Acid phosphatase can be considered as a marker enzyme for yeast cell vacuoles.

Mol Gen Genet, 1979 Nov, 176(3), 393 - 8
Ozone response in wild type and radiation-sensitive mutants of Saccharomyces cerevisiae; Dubeau H et al.; The effect of ozone exposure on Saccharomyces cerevisiae was studied . Factors such as ozone concentration, treatment time, media, initial cell concentration and growth phase were shown to influence ozone response in this organism . Logarithmic phase cells were much more sensitive than stationary phase cells to the lethal effect of ozone . The radiation-sensitive mutants rad3, rad6, rad51 and rad52 of S . cerevisiae were exposed, in water, to 50 ppm of ozone for 30 min . On comparing their survival curves, the rad51 and the rad52 mutants showed a greater sensitivity to ozone exposure than the wild type.

Cell, 1979 Nov, 18(3), 623 - 35
Recovery of S . cerevisiae a cells from G1 arrest by alpha factor pheromone requires endopeptidase action; Ciejek E et al.; Radioactive alpha factor is degraded to discrete biologically inactive fragments by the target a cells of S . cerevisiae, but not by alpha cells which make the pheromone . The pattern of cleavage products and sequence analysis of one fragment indicated that the first scission occurred between leucine 6 and lysine 7 . The protease inhibitors tosyl-L-argininyl-methyl ester (TAME), tosyl-L-lysyl-chloromethylketone (TLCK) and N-acetyl-L-leucyl-L-leucyl-L-argininal (leupeptin) markedly prolonged the period of G1 arrest in a cells exposed to alpha factor, while other standard protease inhibitors had little or no effect . The presence of TAME and leupeptin, or TLCK, reduced the rate of degradation of radioactively labeled alpha factor by a cells . Intact yeast cells have apparent esterase and amidase activities that are blocked by the same spectrum of inhibitors that potentiate alpha factor action . Purified alpha factor is a competitive inhibitor of these hydrolytic activities . The activities are present in yeast mutants which have greatly reduced levels of the three major vacuole-associated proteases (A, B and C) or which carry an ochre mutation in the major neutral protease (B) . These observations indicate that the inactivation of alpha factor is due to endoproteolytic cleavage, the destruction of the pheromone is required to overcome its effects on growth and that degradation of the molecule may involve surface bound endopeptidase(s).

J Bacteriol, 1979 Oct, 140(1), 73 - 82
Chimeric plasmids for cloning of deoxyribonucleic acid sequences in Saccharomyces cerevisiae; Storms RK et al.; Two sets of plasmids, each carrying a Saccharomyces cerevisiae gene and a portion or all of the yeast 2-micron circle linked to the Escherichia coli plasmid pBR322, have been constructed . One of these sets contains a BamHI fragment of S . cerevisiae deoxyribonucleic acid that includes the yeast his3 gene, whereas the other set contains a BamHI fragment of S . cerevisiae that includes the yeast leu2 gene . All plasmids transform S . cerevisiae and E . coli with a high frequency, possess unique restriction endonuclease sites, and are retrievable from both host organisms . Plasmids carrying the 2.4-megadalton EcoRI fragment of the 2-micron circle transform yeast with 2- to 10-fold greater frequency than those carrying the 1.5-megadalton EcoRI fragment of the 2-micron circle . Restriction endonuclease analysis of plasmics retrieved from S . cerevisiae transformed with plasmics carrying the 2.4-megadalton EcoRI fragment showed that in 13 of 96 cases the original plasmic has acquired an additional copy of the 2-mcron circle . These altered plasmids appear to have arisen by means of an interplasmid recombination event while in S . cerevisiae . A clone bank of S . cerevisiae genes based upon one of these composite plasmids has been constructed . By using this bank and selecting directly in S . cerevisiae, the ura3, tyr1, and met2 genes have been cloned.

Cell, 1979 Oct, 18(2), 309 - 19
Isolation of a circular derivative of yeast chromosome III: implications for the mechanism of mating type interconversion; Strathern JN et al.; We describe genetic and physical characterization of rearrangements of chromosome III which result in changes of cell type in S . cerevisiae . Two types of rearrangements were obtained as rare events which caused a change at the locus controlling cell type, MAT, associated with a recessive lethal mutation, in one case from MATalpha to MATa-lethal, and in the other case from MATa to MATalpha-lethal . The MATa-lethal mutation is a deletion on the right arm of chromosome III, which we demonstrate extends to (or near) HMalpha . We suggest this deletion removes MATalpha and activates cryptic MATa information stored in HMalpha as proposed in the cassette model of mating type interconversion . The MATalpha-lethal mutation is the result of the formation of a circular chromosome III, which we interpret to remove MATa and activate the cryptic MATalpha information stored at HMa . Strains carrying the MATalpha-lethal chromosome contain a circular chromosome of length 62.6 plus or minus 5.7 mum, which is absent in related strains . This chromosome was confirmed to be chromosome III by hybridization of specific yeast DNA fragments to supercoiled DNA obtained from MATalpha-lethal strains . The isolation of a large circular derivative of chromosome III allows correlation of genetic and physical distance based on large distances-1 centimorgan corresponds to approximately 2700 base pairs.

Cell, 1979 Sep, 18(1), 47 - 53
Assembly of the mitochondrial membrane system: sequences of yeast mitochondrial valine and an unusual threonine tRNA gene; Li M et al.; The mitochondrial DNA segments of two independently isolated rho- clones of S . cerevisiae carrying a genetic marker for a threonine tRNA have been characterized by restriction endonuclease analysis and DNA sequencing . The DNA sequences of the two segments have been used to deduce the primary and secondary structures of the tRNA . The threonine tRNA is unusual in having a leucine anticodon (3'-GAU-5') . Despite the anomalous anticodon, the tRNA is proposed to function in mitochondrial protein synthesis . One of the rho- clones contains an additional coding sequence that has been identified as a valine tRNA genes have been located on the wild-type physical map and determined to be transcribed from two different strands.

Cell, 1979 Sep, 18(1), 27 - 35
Splicing of yeast tRNA precursors: a two-stage reaction; Peebles CL et al.; Soluble extracts of S . cerevisiae splice tRNA precursors which contain intervening sequences . The reaction goes to completion and requires ATP for the production of mature sequence tRNA . In the absence of ATP, half-tRNA molecules accumulate . Similar half-tRNA molecules appear as kinetic intermediates and accumulate if splicing is inhibited with pure, mature tRNA . Half-tRNA molecules have been purified . These half-tRNAs are efficiently ligated in an ATP-dependent reaction that is inhibited by added mature tRNA . The product of ligation is the expected mature sequence tRNA . The excised intervening sequence has also been identified . These results suggest an enzymatic mechanism for splicing which involves two independent steps.

Cell, 1979 Sep, 18(1), 11 - 26
A precursor to a minor species of yeast tRNASer contains an intervening sequence; Etcheverry T et al.; Certain tRNAs in S . cerevisiae (tRNATyr and tRNAPhe) arise via precursor molecules which are mature at the 5' and 3' termini but contain intervening sequences adjacent to the anticodon (Knapp et al., 1978; O'Farrell et al., 1978) . In addition to these molecules, precursors to several other tRNAs accumulate in a temperature-sensitive mutant (ts136) at the nonpermissive temperature . We have analyzed one of these species and shown that it is a precursor to a minor species of tRNASer . This precursor is also mature at both termini and contains an intervening sequence of 19 nucleotides adjacent to the hypermodified A residue 3' to the anticodon . The sequence can be arranged in a secondary structure in which the anticodon stem is extended by additional base-pairing, and contains the sites of excision and ligation within two looped regions . Support for this structure was provided by analysis of the products of limited digestion with RNAase T1 . recently Piper (1978) reported the isolation of a minor species of tRNASer which decodes UCG . He found this species to be structurally heterogeneous and determined that the less abundant form corresponds to the tRNA which is altered in the recessive lethal SUP-RL1 amber suppressor . Our data now suggest that the more abundant form may be restricted to reading UCA in vivo; thus mutation of the minor species would result in complete loss of UCG-decoding ability and explain the recessive lethality of SUP-RL1 . We have shown that the precursor which accumulates in ts136 corresponds exclusively to this minor tRNASerUCG species . Our results suggest that this may be the only gene for tRNASer in yeast which contains an intervening sequence.

Mol Gen Genet, 1979 Aug, 175(1), 1 - 4
Two isoaccepting seryl tRNAs coded by separate mitochondrial genes in yeast; Colletti E et al.; In S . cerevisiae four isoacceptor mitochondrial tRNAs for serine have been separated by reversed phase chromatography . At least two of these species are products of different genes . In this work the deletion mapping technique has been used to locate two genes for tRNAser . The gene for tRNAser previously localized in the oli I region of the mitochondrial genome has been found to code for tRNAser2, and another gene coding for tRNAser1 has been detected in the region where most of other tRNA genes are found . Results of fine mapping experiments allowed to localize this gene in the proximity of the gene for tRNAarg.

Mol Gen Genet, 1979 Jul 24, 174(3), 335 - 7
The nucleotide sequence of the mitochondrial genome of a spontaneous "petite" mutant of yeast; Gaillard C et al.; The nucleotide sequence of the repeat unit of the mitochondrial genome of a spontaneous petite mutant of S . cerevisiae is reported . The sequence provides direct information on the AT-spacers and GC-clusters of the mitochondrial genome of yeast.

Genetics, 1979 Jul, 92(3), 803 - 21
Mapping chromosomal genes of Saccharomyces cerevisiae using an improved genetic mapping method; Wickner RB; A triploid (3n) strain of Saccharomyces cerevisiae was constructed carrying a standard marker on each of chromosomes 1 through XVII in the -/+/+ configuration . This is called a "supertriploid." Meiotic spores from this strain (n + approximately n/2) were mated with a haploid (n) carrying an unmapped mutation . Meiotic analysis of each zygote clone (2n + approximately n/2) produced in this way resulted in elimination of an average of 4.2 chromosomes as the possible location of the unmapped marker . The distribution of extra chromosomes in the 2n + approximately n/2) strains was nearly random . Meiotic segregrants of these crosses carrying the unmapped mutation in the -/+ configuration were then crossed with multiply marked haploid strains to further narrow the possible location of the unmapped mutation to a single chromosome . Scoring of markers by complemention tests was simplified by mating spore clones with mixtures of a and alpha strains, each pair carrying the same set of markers . Using this new, more rapid method ("supertriploid mapping"), eight genes required for the maintenance of the killer plasmid were located on the genetic map of S . cerevisiae.

Mutat Res, 1979 Jul, 61(2), 191 - 6
Sodium azide-induced mutagenesis in Saccharomyces cerevisiae; Silhankova L et al.; Sodium azide (0.5--2.0 X 10(-5) M), applied for 24 h on cells growing in complete medium, increased up to 26 times the frequency of reversions and locus-specific suppressor mutations of allele ilv1-92 in diploid strain D7 of Saccharomyces cerevisiae . Similarly, it enhanced the frequency of reversions and/or mitotic gene conversions of alleles trp5-12/trp5-27 up to 19 times . Reconstruction experiments showed that the increase of mutations in complete medium was not due to a selection of prototrophic types under growth conditions and, therefore, that sodium azide acts as a weak mutagen in S . cerevisiae under growth conditions at a low pH . No mutagenic or convertogenic effect was observed when azide was applied to resting cells in buffer at pH 4.2.

J Bacteriol, 1979 Jun, 138(3), 799 - 804
Modulation of cytochrome biosynthesis in yeast by antimetabolite action of levulinic acid; Malamud DR et al.; Levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, was used to inhibit cytochrome biosynthesis in growing yeast cells . In Saccharomyces cerevisiae the antimetabolite acts by inhibiting delta-aminolevulinic acid dehydratase in vivo, causing an accumulation of intracellular delta-aminolevulinic acid and simultaneous decreases in all classes of mitochondrial cytochromes . Changes in cellular cytochrome content with increasing levulinic acid concentration suggested the existence of different regulatory patterns in S . cerevisiae and Candida utilis . In C . utilis, cytochrome a.a3 formation is very resistant to the antimetabolite action of levulinic acid . In this aerobic yeast, cytochrome c+c1 is the most sensitive to levulinic acid, and cytochrome b exhibits intermediate sensitivity.

Mol Cell Biochem, 1979 May 6, 25(1), 33 - 42
Mitochondrial glucose-6-phosphate dehydrogenase from Saccharomyces cerevisiae; Campbell WH et al.; In Saccharomyces cerevisiae, a small proportion of the glucose-6-P dehydrogenase activity is firmly associated with the mitochondrial fraction and is not removed by repeated washing or density-gradient centrifugation . However, the enzyme is released by sonic disruption . Mitochondrial glucose-6-P dehydrogenase that is released by sonication and partially purified has been found to be similar to cytosol glucose-6-P dehydrogenase with respect to electrophoretic mobility, isoelectric point, pH optimum, molecular size, and apparent KM's for NADP+ and glucose-6-P . These results indicate that a single species of glucose-6-P dehydrogenase is synthesized in S . cerevisiae and that the enzyme has more than one intracellular location . Mitochondrial glucose-6-P dehydrogenase may be a source of intramitochondrial NADPH and may function with hexokinase and transhydrogenase to provide a pathway for glucose oxidation that is coupled to the synthesis of mitochondrial ATP . A constant proportion of total glucose-6-P dehydrogenase activity remains compartmented in the mitochondrial fraction throughout the growth cycle.

Cell, 1979 May, 17(1), 185 - 90
Deletions of a tyrosine tRNA gene in S . cerevisiae; Rothstein R; Genetic fine structure analysis of a tyrosine tRNA in yeast revealed that complete deletions of the gene occurred at an unusually high frequency . Among 56 spontaneous mutations at the SUP4 locus, 16 were classified as deletions as judged by their failure to recombine with any other mutations known to map within the gene . Physical analysis of each deletion confirmed the genetic result . The deletions fall into two size classes: ten are 2100 bp deletions and six are 2800 bp deletions . These results imply that the physical structure of the region surrounding the SUP4 locus, which is known to contain short repeated segments, has a direct role in promoting deletions.

J Membr Biol, 1979 Apr 20, 46(2), 91 - 124
Water permeability of yeast cells at sub-zero temperatures; Levin RL et al.; A combined cryomicroscopic-multiple nonlinear regression analysis technique has been used to determine the water permeability of the yeast cell Saccharomyces cerevisiae during freezing . The time rate of change in volume of "supercooled" yeast cells was photographically monitored using a "cryomicroscope" which is capable of controlling in a programmable manner both the temperature and the time rate of change in temperature of the cell suspension being studied . Multiple nonlinear regression analysis together with a thermodynamic model of cell water transport during freezing was then used to statistically deduce the subzero temperature dependence of the cell water permeability . The water permeability process for S . cerevisiae being cooled at subzero temperatures was found to be rate-limited by the passage of water through either the plasmalemma, the cell wall, or a combination of these two permeability barriers . The hydraulic water permeability coefficient for yeast at 20 degrees C is approximately 1--2 x 10(-13) cm3/dyne sec, if extrapolation from subzero temperatures to room temperature is permissible, while the apparent activation energy governing the permeability process at subzero temperatures is approximately 45--68 kJ/mol (11--16 kcal/mol).

Cell, 1979 Apr, 16(4), 827 - 39
Identification and mapping of the transcriptional and translational products of the yeast plasmid, 2mu circle; Broach JR et al.; We have identified two major and approximately ten minor poly(A)-containing RNA species in S . cerevisiae which arise from in vivo transcription of the yeast plasmid, known as 2mu circle . The two major species, which are 1325 and 1275 bases in length, are transcribed from the two unique halves of the plasmid and extend into the inverted repeat sequences which separate the unique regions . The map positions of the minor transcripts, which range in length from 350 to 2600 bases, indicate that except for a small region of the genome in which no transcription is observed, both strands of the entire 2mu circle genome are transcribed . We also present evidence demonstrating that RNA transcribed from 2mu circular DNA is used to program the synthesis of specific proteins in yeast: that is, yeast RNA complementary to 2mu circle DNA can be translated in vitro to produce specific polypeptides of substantial size . Finally, the pattern of transcription of 2mu circle suggests the possibility that messenger RNA species are derived by cleavage of larger transcripts, and in addition, that the intramolecular recombination of 2mu circle which occurs in yeast functions as a genetic switch to allow separate expression of two sets of genes on the 2mu circle genome.

Cell, 1979 Apr, 16(4), 739 - 51
Evidence for transposition of dispersed repetitive DNA families in yeast; Cameron JR et al.; Dispersed repetitive DNA sequences from yeast (Saccharomyces cerevisiae) nuclear DNA have been isolated as molecular hybrids in lambdagt . Related S . cerevisiae strains show marked alterations in the size of the restriction fragments containing these repetitive DNAs . "Ty1" is one such family of repeated sequences in yeast and consists of a 5.6 kilobase (kb) sequence including a noninverted 0.25 kb sequence of another repetitious family, "delta", on each end . There are about 35 copies of Ty1 and at least 100 copies of delta (not always associated with Ty1) in the haploid genome . A few Ty1 elements are tandem and/or circular, but most are disperse and show (along with delta) some sequence divergence between repeat units . Sequence alterations involving Ty1 elements have been found during the continual propagation of a single yeast clone over the course of a month . One region with a large number of delta sequences (SUP4) also shows a high frequency of sequence alterations when different strains are compared . One of the differences between two such strains involves the presence or absence of a Ty1 element . The novel joint is at one inverted pair of delta sequences.

Mol Gen Genet, 1979 Mar 27, 171(3), 239 - 50
Mitochondrial DNA from Podospora anserina . II . Properties of mutant DNA and multimeric circular DNA from senescent cultures; Cummings DJ et al.; Mitochondrial (Mt) DNA from mitochondrial mutants of race s Podospora anserina and from senescent cultures of races s and A was examined . In mutants, we observed that fewer full length circles (31 mu) were present; instead, smaller circles characteristic for each mutant studied were found . Eco R1 digestion of these mutant MtDNAs indicated that in certain mutants, although specific fragments were absent, the total molecular weight of the fragments was not much different than wild-type . The properties of senescent MtDNA was strikingly different from either wild-type or mutant Mt DNA . First, a multimeric set of circular DNA was observed for both race s and A, with a monomeric repeat size of 0.89 mu . These circles ranged in size from 0.89 mu to greater than 20 mu; only one molecule out of some 200 molecules was thought to be of full length (31 mu) . Density gradient analysis showed that there were two density species: a majority were at the same density as wild-type (1.694 g/cm3) and a second at 1.699 g/cm3 . Most of the circular molecules from MtDNA isolated by either total DNA extraction or by extraction of DNA from isolated mitochondria were contained in the heavy DNA fraction . Eco R1 enzymatic digestion indicated that the light DNA had several fragments (amounting to about 23 x 10(6) daltons) missing, compared with young, wild-type MtDNA . Heavy senescent MtDNA was not cleaved by Eco R1 . Analysis with Hae III restriction endonuclease showed also that light senescent MtDNA was missing certain fragments . Heavy MtDNA of average size 20 x 10(6) daltons, yielded only one fragment, 2,500 bp long, by digestion with Hae III restriction endonuclease . Digestion of heavy DNA with Alu I enzyme yielded 10 fragments totalling 2,570 bp . By three criteria, electron-microscopy, Eco R1 and Hae digestion, we conclude that the heavy MtDNA isolated from senescent cultures of Podospora anserina consisted of a monomeric tandemly repeating subunit of about 2,600 bp length . These results on the properties of senescent MtDNA are discussed with regard to the published properties of the rho- mutation in the yeast, S . cerevisiae.

J Bacteriol, 1979 Mar, 137(3), 1185 - 90
Synthesis and modification of proteins during the cell cycle of the yeast Saccharomyces cerevisiae; Elliott SG et al.; We have used a novel technique to study the synthesis, modification and degradation of proteins during the cell cycle in Saccharomyces cerevisiae . Logarithmically growing cells were pulse-labeled twice, with the pulses separated in time by more than one generation . Subsequently, the cells were fractionated as to their position in the cell cycle by centrifugal elutriation, and for different proteins the ratio of radioactive material from the two pulses was then determined . Periodic degradation, synthesis, or modification would produce periodic variations in the ratio of counts . Two-dimensional gel electrophoresis was used to examine 110 different proteins at different times of the cell cycle . All but two proteins had a constant ratio of counts through the cell cycle . This indicates that the rate of synthesis of individual proteins increases exponentially during the cell cycle and that periodic degradation or modification of proteins is not a general feature of the cell cycle in S . cerevisiae.

Mol Gen Genet, 1979 Feb 26, 170(2), 225 - 30
Peptide chain elongation rate and ribosomal activity in Saccharomyces cerevisiae as a function of the growth rate; Bonven B et al.; The peptide-chain elongation rate of Saccharomyces cerevisiae at two different growth rates was estimated by the kinetics of radioactive labelling of nascent and finished polypeptides as described by Gausing, 1972, and Young and Bremer, 1976 . The elongation rates of a diploid strain cultured in yeast nitrogen base supplemented with glucose or acetate were 9.3 amino acids/s and 5.5 amino acids/s at 30 degrees C, respectively . These data together with published values on the "ribosomal efficency" as a function of growth rate (Waldron and Lacroute, (1975) enable us to estimate the rate of synthesis of ribosomal proteins as a function of the rate of total protein synthesis, alpha r, and the fraction of ribosomes that one active in protein synthesis . We conclude that in S . cerevisiae alpha r is largely independent of the growth rate while the fraction of active ribosomes decreases with decreasing growth rate.

Mol Gen Genet, 1979 Feb 16, 170(1), 25 - 48
Physical mapping of the yeast mitochondrial genome: derivation of the fine structure and gene map of strain D273-10B and comparison with a strain (MH41-7B) differing in genome size; Morimoto R et al.; (1) We have derived a fine-structure map of the 70 kb mitochondrial genome of the yeast S . cerevisiae, strain D273-10B, and compared it with our previous maps for strain MH41-7B . Restriction fragment maps for 56 enzyme recognition sites for 13 endonucleases, Eco RI, Hpa I, Bam HI, Hha I, Hinc II, Xba I, Hind III, Bgl II, Pvu II, Sal I, Pst I, Sst I, and Xho I, have been derived . We have used several methods to obtain these maps: (a) Four enzymes (Sal I, Sst I, Xho I, Pst I), each of which cuts D273-10B mtDNA at a single site, were employed to localize and orient fragments from multi-site enzyme digests that are cleaved by the single-site enzyme . (b) Radioactively labeled probes (rRNA or copy RNA {cRNA} transcribed from simple-sequence petite mtDNA) were hybridized to restriction fragments from different digests for identification of fragments which share common sequences . (c) The products of double or triple enzyme digests were identified for mapping and confirmation of the localization of restriction sites . (2) The antibiotic-resistant (antR) loci for erythromycin (E), chloramphenicol (C), paromomycin (P), and oligomycin (OI, OII) were positioned on the physical restriction map by hybridization of 3H-labeled cRNA transcribed from simple-sequence petite mtDNAs that retain a single genetic antR marker to appropriate restriction fragments bound to nitrocellulose filters . (3) Mitochondrial transcripts (21s rRNA, 14s rRNA, and tRNAs) labeled with 125I were hybridized to restriction fragments for identification of the corresponding coding sequence . (4) The gene order and localization of the antR loci and mitochondrial transcripts are as follows: C(0-1.5u)-tRNA I(0-21.5u)-P(29-36.6u)-tRNA II(29-46.4u)-14s rRNA(36-38.3u)-OII(60.3-62.5u) - tRNA III(73-76u) - OI(78.6-83.0u) - tRNA IV(82.5-83.0u) - E(94.2-98.6u) - 21s rRNA (94.2-99.4u) . (5) The DNA fine structure and gene map of the 70 kb D273-10B mtDNA were compared to the map of the larger MH41-7B (76 kb) mtDNA . There are 56 restriction sites on D273-10B and 67 sites on MH41-7B for the 13 enzymes studied . The additional restriction sites are largely accounted for by the presence, in MH41-7B, of two sets of sequences, "A" (2.7 kb) and "B" (3.0 kb), located on either side of the OII marker . The remainder of the fragments map is remarkably similar for the two strains . The distances separating the antR loci and the mitochondrial transcripts are very similar except in the two regions surrounding OII.

Mol Gen Genet, 1979 Feb 16, 170(1), 11 - 23
Physical mapping of the Xba I, Hinc II, Bgl II, Xho I, Sst I, and Pvu II restriction endonuclease cleavage fragments of mitochondrial DNA of S . cerevisiae; Morimoto R et al.; A detailed molecular dissection of the yeast mitochondrial genome can be made with restriction endonucleases that generate site-specific cuts in DNA . The ordering of restriction fragments provides the basis of the physical mapping of mitochondrial transcripts and antibiotic resistance (antR) loci, and is a means of analyzing the molecular organization of mtDNA of petite and mit- deletion mutants . We have previously mapped the sites in the mtDNA of yeast strain MH41-7B recognized by the endonucleases Eco RI, Hpa I, Hind III, Bam HI, Sal I, Pst I, and Hha I, providing a total of 41 cleavage sites . We have now mapped the sites recognized by the endonucleases Xba I, Hinc II, Bgl II, Pvu II, Xho I, and Sst I, which make 6, 13, 5, 6, 2, and 2 cuts, respectively . Fragment maps for each of these endonuclease sites were derived by analysis of the products of double-enzyme digests and by hybridization of 3H-cRNA probes transcribed from low-kinetic-complexity petite mtDNAs to restriction fragments generated by various combinations of enzymes.

Biochim Biophys Acta, 1979 Jan 11, 545(1), 1 - 14
The yeast mitochondrial ATPase complex . Subunit composition and evidence for a latent protease contaminant; Ryrie IJ et al.; 1 . The subunit compositions of the F1 (oligomycin-insensitive) and F1--F0 (oligomycin-sensitive) mitochondrial ATPase complexes from Saccharomyces cerevisiae have been examined by the highly resolving technique of sodium dodecyl sulphate-polyacrylamide slab gel electrophoresis using a discontinuous buffer system . When isolated in the presence of protease inhibitors, F1 and F1--F0 contained five and twelve bands, respectively; this contrasts with the four- and ten-band patterns seen previously using the less resolving disc gel method . When isolated in the absence of protease inhibitors both F1 and F1--F0 contain spurious polypeptides produced by proteolytic modification . 2 . Endogenous protein turnover in S . cerevisiae was impaired in the presence of protease inhibitors . F1--F0 isolated from cells grown in the presence and absence of inhibitors contained an identical polypeptide composition, suggesting that the subunits are not significantly modified by endogenous proteases prior to cell harvesting . 3 . Yeast F1--F0 prepared in the presence of protease inhibitors contains a latent, sodium dodecyl sulphate-activated protease contaminant . Sodium dodecyl sulphate-induced proteolysis is largely confined to the 52 000 dalton alpha subunit which degrades into polypeptides of 40 000 and 10 700 daltons . The 40 000 dalton band is apparently equivalent to the polypeptide previously designated subunit 3 . 4 . Both F1 and F1--F0 were isolated from Torulopsis glabrata, a yeast with considerably shorter mitochondrial DNA than that in S . cerevisiae . F1--F0 catalysed high rates of ATP--32Pi exchange when reconstituted into phospholipid vesicles, thus demonstrating the presence of a complete coupling mechanism . F1--F0 contained approximately twelve subunits and F1 five, like the S . cerevisiae complexes . It therefore appears that the shorter mitochondrial DNA length does not produce a significantly simpler ATPase subunit structure.

Mol Gen Genet, 1979 Jan 10, 168(2), 125 - 39
Evidence that induction and suppression of mutations and recombinations by chemical mutagens in S . cerevisiae during mitosis are jointly correlated; Fahrig R; Mutagen-induced intergenic and interallelic recombination as well as forward mutation were studied in one and the same strain of S . cerevisiae . In nontoxic dose ranges, the induction of mutants and recombinants was parallel after treatment with ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), N-methyl-N'-nitro-M-nitrosoguanidine (MNNG), triethylene melamine (TEM), 4-nitroquinoline 1-oxide (4-NQO), sodium nitrite (NaNO2), and 1-fluoro-2,4-dinitrobenzene (2,4-DNFB) . Acridine orange (AO) after treatment without light induced recombinants, but reduced the frequency of spontaneous mutations . In combination with TEM, AO exerted the same effect, i.e., reduced its mutagenic effect and enhanced its recombinogenic effect . 4,5,6-Trichloro-2-(2,4-dichlorophenoxy) phenol (Cl5-predioxin) induced mutants and intergenic recombinants, but specifically reduced the spontaneous frequency of interallelic recombinants . In combination with TEM, it enhanced its mutagenic and intergenic recombinogenic effects but reduced its interallelic recombinogenic effect . The main conclusions of the present study, that is 1 . Essentially similar lesions can lead to different genetic consequences, and 2 . Induction of mutation and recombination are jointly correlated, i.e., suppression of mutations leads to an enhancement of recombinations, while suppression of recombinations leads to an enhancement of mutations, are used to set up a speculative concept for mutation and recombination induction in the diploid yeast cell during mitosis.

Mol Gen Genet, 1979 Jan 2, 167(3), 287 - 98
Genetic localization of diuron- and mucidin-resistant mutants relative to a group of loci of the mitochondrial DNA controlling coenzyme QH2-cytochrome c reductase in Saccharomyces cerevisiae; Colson AM et al.; Diuron-resistance, DIU (Colson et al., 1977), antimycin-resistance, ANA (Michaelis, 1976; Burger et al., 1976), funiculosin-resistance, FUN (Pratje and Michaelis, 1977; Burger et al., 1977) and mucidin-resistance, MUC (Subik et al., 1977) are each coded by a pair of genetic loci on the mit DNA of S . cerevisiae . In the present paper, these respiratiory-competent, drug-resistant loci are localized relative to respiratory-deficient BOX mutants deficient in coenzyme QH2-cytochrome c reductase (Kotylak and Slonimski, 1976, 1977) using deletion and recombination mapping . Three drug-resistant loci possessing distinct mutated allelic forms are distinguished . DIU1 is allelic or closely linked to ANA2, FUN1 and BOX1; DIU2 is allelic or closely linked to ANA1, MUC1 and BOX4/5; MUC2 is allelic to BOX6 . The high recombinant frequencies observed between the three loci (13% on the average for 33 various combinations analyzed) suggest the existence of either three genes coding for three distinct polypeptides or of a single gene coding for a single polypeptide but subdivided into three easily separable segments . The resistance of the respiratory-chain observed in vitro in the drug-resistant mutants and the allelism relationships between respiratory-competent, drug-resistant loci and coQH2-cyt c reductase deficient, BOX, loci strongly suggest that each of the three drug-resistant loci codes for a structural gene-product which is essential for the normal coQH2-cyt c reductase activity and is obviously a good candidate for a gene product of the drug-resistant loci mapped in this paper . Polypeptide length modifications of cytochrome b were observed in mutants deficient in the coQH2-cyt c red and localized at the BOX1, BOX4 and BOX6 genetic loci (Claisse et al., 1977, 1978) which are precisely the loci allelic to drug resistant mutants as shown in the present work . Taken together these two sets of data provide a strong evidence in favor of the idea that there exist three non contiguous segments of the mitochondrial DNA sequence which code for a single polypeptide sequence of cytochrome b . In each segment mutations which modify the polypeptide sequence can occur leading to the loss (BOX mutants) or to a modification (drug resistant mutants) of the enzyme activity.

J Supramol Struct, 1979, 12(4), 425 - 33
Sequence of the amino-terminal region of rat liver ribosomal proteins S4, S6, S8, L6, L7a, L18, L27, L30, L37, L37a, and L39; Wittmann-Liebold B et al.; The sequence of the amino-terminal region of eleven rat liver ribosomal proteins--S4, S6, S8, L6, L7a, L18, L27, L30, L37a, and L39--was determined . The analysis confirmed the homogeneity of the proteins and suggests that they are unique, since no extensive common sequences were found . The N-terminal regions of the rat liver proteins were compared with amino acid sequences in Saccharomyces cerevisiae and in Escherichia coli ribosomal proteins . It seems likely that the proteins L37 from rat liver and Y55 from yeast ribosomes are homologous . It is possible that rat liver L7a or L37a or both are related to S cerevisiae Y44, although the similar sequences are at the amino-terminus of the rat liver proteins and in an internal region of Y44 . A number of similarities in the sequences of rat liver and E coli ribosomal proteins have been found; however, it is not yet possible to say whether they connote a common ancestry.

J Environ Pathol Toxicol, 1979 Jan-Feb, 2(3), 657 - 70
Comparison of the genetic activity of 5-nitroimidazole derivatives in Escherichia coli, Neurospora crassa, Saccharomyces cerevisiae and Drosophila melanogaster; Mohn GR et al.; 5-nitroimidazoles, including metronidazole (compound 1) and 3 analogues (compounds 2, 3 and 4) of actual or potential chemotherapeutic use were assayed for genetic activity in test systems detecting forward and back mutations in Escherichia coli K-12/343/113, forward mutations in Neurospora crassa heterokaryon 12, mitotic gene conversion in the heteroallelic diploid yeast strain Saccharomyces cerevisiae D4 and sex-linked recessive lethals in Drosophila melanogaster . Whereas metronidazole exhibits moderate mutagenic activity in E . coli, two of the analogues, compounds 2 and 3 are strongly mutagenic even at concentrations that do not inactive the colony forming ability of the cells . The analogue compound 4 does not show any effect toward E . coli under the present experimental conditions . Similar results were obtained with N . crassa, with S . cerevisiae and with Drosophila in which compound 2 exhibits the highest effect, while compound 4 is non-mutagenic in all assays . These biological effects have been partly explained on the basis of differences in the chemical structure of the compounds.

Med Microbiol Immunol (Berl), 1979, 167(4), 211 - 22
{Cross reactions of eight yeasts and their importance in serological Candida diagnostic (author's transl)}; Muller HL; While the antigen structure of yeast cell walls is well known, the immunological cross reactivity of these is often difficult to interpret . The cross reactions of eight yeasts were tested in rabbit hyperimmune sera by the indirect immunofluorescence test . Among the eight species examined were the medically important yeasts C . albicans, C . pseudotropicalis, C . krusei, C . parapsilosis, C . tropicalis, T . glabrata, and C . guilliermondii and the apathogenic yeast S . cerevisiae . It has been shown, that there is no correlation between the number of common antigens and the degree of cross reactivity which give identical titers . Therefore it appears, that the quantitative contributions of the single antigens have an important rule, i.e., some antigens are immunogenic in one species while having only hapten characteristics in another . Further the results show that in infections with C . krusei, C . pseudotropicalis, and C . guilliermondii homologous antigens have to be used for the serological diagnosis . The testing of human sera with the yeast antigens by the same methods showed that the strikingly distributions of the Candida titer and the Saccharomyces titer were similar . A larger number of sera of healthy people and patients were compared in the hemagglutination test . These results showed that pathological C . albicans titers cannot be caused by S, cerevisiae antibodies.

Mol Gen Genet, 1979, 172(3), 259 - 69
Studies on the induction of petite mutants in yeast by analogues of berenil . Characterization of three mutants resistant to the compound Hoe 15,030; Vaughan PR et al.; Compound Hoe 15,030 is an analogue of berenil which is as effective as berenil in inducing petite mutants in Saccharomyces cerevisiae . Hoe 15,030 has greater stability than berenil in aqueous solution, and is less toxic to yeast at high drug concentrations . Mutants of S . cerevisiae strain J69-1B have been isolated which are resistant to the petite inducing effects of Hoe 15,030 . Three mutant strains (HR7, HR8 and HR10) were characterized and each was shown to carry a recessive nuclear mutation determining resistance to Hoe 15,030 . The degree of resistance to Hoe 15,030 is different for each mutant, and each was found to be co-ordinately cross-resistant both to berenil and to another analogue of berenil, Hoe 13,548 . However, the three mutants show no cross-resistance to other unrelated petite inducing drugs, including ethidium bromide, euflavine and 1-methyl phenyl neutral red . Further studies on the mutants revealed that each strain exhibits characteristic new properties indicative of changes in mitochondrial membrane functions concerned with the replication (and probably also repair) of mitochondrial DNA . Thus, mutant HR7 is hypersensitive to petite induction by the detergent sodium dodecyl sulphate under conditions where the parent J69-1B is unaffected by this agent . Mutant HR8 is even more sensitive to sodium dodecyl sulphate than is HR7, and additionally shows a markedly elevated spontaneous petite frequency . Isolated mitochondria from strains HR8 and HR10 (but not HR7) show resistance to the inhibitory effects of Hoe 15,030 on the replication of mitochondrial DNA in vitro.

Z Allg Mikrobiol, 1979, 19(7), 455 - 65
Ultracytochemical characterization of non-specific acid phosphatase activities in Saccharomyces cerevisiae; Bohm KJ et al.; Glutaraldehyde prefixation causes a considerable inactivation of the acid phosphatase of yeast protoplasts in dependence on the duration of aldehyde influence . Lead ions necessary for ultracytochemical demonstration effect a still stronger inhibition of enzymatic activity . Prefixation, however, protects the enzyme from further inhibition by lead . At pH 4.4 in intact cells acid phosphatase activities are mainly localized in the periplasmic space and in vesicles fused with the plasma membrane . The cell wall and cytoplasm usually remain free of reaction products . On the cell surface activities are found in form of globular lead deposits . At pH 5.2 and 6.3 the periplasmic activity appears decreased compared to that at lower pH values and the intracellular activity is increased . The plasma membrane of protoplasts is completely free of precipitates . The intracellular activity sites of protoplasts (cisternae of endoplasmic reticulum and/or Golgi-like system, small vesicles, central vacuole, nuclear envelope) are the same as for intact cells . The occurrence of at least two forms of acid phosphatase in S . cerevisiae id deduced.

J Bacteriol, 1978 Dec, 136(3), 1174 - 7
Isolation of a peptide transport-deficient mutant of yeast; Marder R et al.; A peptide transport mutant of a leucine-lysine auxotroph of Saccharomyces cerevisiae (strain Z1-2D) was isolated on the basis of its resistance to L-ethionyl-L-alanine . The mutant, designated Z1-2D Etar, did not utilize di- and tripeptides containing leucine or lysine although it contained peptidases which released the required amino acids from these substrates . S . cerevisiae Z1-2D Etar did not accumulate radioactivity from {14C}glycyl-L-leucine under conditions identical to those in which the parent took up the label from this dipeptide . These results indicate that the mutant lacks the cellular mechanism to transport peptides to the site of the peptidase activity and that di- and tripeptides share a common mode of entry into yeast.

Mutat Res, 1978 Nov, 58(2-3), 133 - 42
Absence of mutagenicity of praziquantel, a new, effective, anti-schistosomal drug, in bacteria, yeasts, insects and mammalian cells; Bartsch H et al.; Praziquantel (Embay 8440, Droncit) a new, effective anti-schistosomal drug, was tested in various short-term assays that have shown a predictive value for the detection of potential carcinogens . Indicator organisms S . typhimurium strains, S . pombe, S . cerevisiae, cultured V79 Chinese hamster cells or human heteroploid cells and Drosophila melanogaster were treated with Praziquantel . The induction of reverse and forward mutations, mitotic gene conversions, X-linked recessive lethals, sister-chromatid exchanges and unscheduled DNA-repair synthesis was scored; rodent-liver microsome-, cell- and host-mediated assays were also performed . Hycanthone, another schistosomicide was included as a positive control . The absence of a genetic activity of Praziquantel uniformly observed in such a battery of tests (i) confirms the assumption that the anti-schistosomal effectiveness of this drug is not related to the mutagenic activity and (ii) should encourage the implementation of extended clinical and field trials.

J Biol Chem, 1978 Sep 25, 253(18), 6484 - 92
Biosynthesis of yeast mannan . Properties of a mannosylphosphate transferase in Saccharomyces cerevisiae; Karson EM et al.; A homogenate of mechanically broken, freshly grown Saccharomyces cerevisiae X2180 cells catalyzes the transfer of mannosylphosphate units from guanosine diphosphate mannose to reduced alpha1 leads to 2-{3H}mannotetraose to yield reduced mannosylphosphoryl {3H}-mannotetraose . The product is analogous in structure to the phosphorylated mannan side chains, which suggests that the enzymic activity is involved in mannoprotein biosynthesis in the intact cell . The mannosylphosphate transferase activity, localized in a membrane fraction obtained by differential centrifugation at 100,000 x g, was solubilized by Triton X-155 and purified 250-fold by ammonium sulfate precipitation and by ion exchange and gell filtration chromatographies . The enzyme requires MN2+ OR Co2+ ions for activity and is stimulated by various detergents . The mnn2 and mnn3 mannan mutants of S . cerevisiae possess normal levels of mannosylphosphate transferase activity, whereas the mnn4 mutant cells contain very low, if any, activity . This is consistent with a previous conclusion that the mnn4 mutation affects the mannosylphosphate transferase activity, whereas the mnn2 and mnn3 strains possess phosphate-deficient mannans because they are unable to synthesize the appropriate side chain precursors . A new mannan mutant class with the mnn4 chemotype was isolated, but the mutation proved to be recessive and nonallelic with the mnn4 locus . This new locus is designated mnn6.

Nature, 1978 Sep 14, 275(5676), 104 - 9
Transformation of yeast by a replicating hybrid plasmid; Beggs JD; Chimaeric plasmids have been constructed containing a yeast plasmid and fragments of yeast nuclear DNA linked to pMB9, a derivative of the ColEl plasmid from E . coli . Two plasmids were isolated which complement leuB mutations in E . coli . These plasmids have been used to develop a method for transforming a leu2 strain of S . cerevisiae to Leu+ with high frequency . The yeast transformants contained multiple plasmid copies which were recovered by transformation in E . coli . The yeast plasmid sequence recombined intramolecularly during propagation in yeast.

J Biol Chem, 1978 Sep 10, 253(17), 6218 - 25
The functional importance of structural features of ergosterol in yeast; Nes WR et al.; As an approach to the study of the relationship between the structure of sterols and their capacity to function in the lipid leaflet of membranes, various sterols were examined for their ability to support the growth of anaerobic Saccharomyces cerevisiae . A marked dependence on precise structural features was observed in growth-response and morphology . Of the chemical groups which distinguish ergosterol, the main sterol of S . cerevisiae, the hydroxyl group at C-3 was obligatory, and the other groups were found to be of the following relative importance: 24beta-methyl-delta22-grouping greater than 24beta-methyl group greater than delta5,7-diene system = delta5-bond approximately or equal to no double bond . Methyl groups at C-4 and C-14 were inconsistent with activity . Consequently, the data strongly suggest that the normal biosynthetic processes removal of methyl groups from the nucleus and introduction of one in the side chain are of functional significance . A double bond between C-17 and C-20 joining the steroidal side chain to the nucleus had no deleterious effect on the growth process but only if C-22 was trans-oriented to C-13 . In the cis-case no growth at all proceeded . This means the natural sterol probably acts functionally in the form of its preferred conformer in which C-22 is to the right ("right-handed") in the usual view . Since the placing of a substituent (OH or CH3) in the molecule at C-20 in such a way that it appears on the front side in the right-handed conformer completely destroyed activity, the sterol apparently presents its front face to protein or phospholipid when complexing occurs.

J Bacteriol, 1978 Aug, 135(2), 498 - 510
Induction and inhibition of the allantoin permease in Saccharomyces cerevisiae; Sumrada R et al.; Allantoin uptake in Saccharomyces cerevisiae is mediated by an energy-dependent, low-Km, active transport system . However, there is at present little information concerning its regulation . In view of this, we investigated the control of alloantoin transport and found that it was regulated quite differently from the other pathway components . Preincubation of appropriate mutant cultures with purified allantoate (commercial preparations contain 17% allantoin), urea, or oxalurate did not significantly increase allantoin uptake . Preincubation with allantoin, however, resulted in a 10- to 15-fold increase in the rate of allantoin accumulation . Two allantoin analogs were also found to elicit dramatic increases in allantoin uptake . Hydantoin and hydantoin acetic acid were able to induce allantoin transport to 63 and 95% of the levels observed with allantoin . Neither of these compounds was able to serve as a sole nitrogen source for S . cerevisiae, and they may be non-metabolizable inducers of the allantoin permease . The rna1 gene product appeared to be required for allantoin permease induction, suggesting that control was exerted at the level of gene expression . In addition, we have shown that allantoin uptake is not unidirectional; efflux merely occurs at a very low rate . Allantoin uptake is also transinhibited by addition of certain amino acids to the culture medium, and several models concerning the operation of such inhibition were discussed.

J Bacteriol, 1978 Aug, 135(2), 490 - 7
Metabolite compartmentation in Saccharomyces cerevisiae; Zacharski CA et al.; Uninduced cultures of Saccharomyces cerevisiae exhibit high basal levels of allantoinase, allantoicase, and ureidoglycolate hydrolase, the enzymes responsible for degrading allantoin to urea . As a result, these activities increase only 4- to 8-fold upon induction, whereas the urea-degrading enzymes, urea carboxylase and allophanate hydrolase, have very low basal levels and routinely increase 30-fold on induction . Differences in the inducibility of these five enzymes were somewhat surprising because they are all part of the same pathway and have the same inducer, allophanate . Our current studies reconcile these observations . S . cerevisiae normally contained up to 1 mM allantoin sequestered in a cellular organelle, most likely the vacuole . Separation of the large amounts of allantoin and the enzymes that degrade it provide the cell with an efficient nitrogen reserve . On starvation, sequestered allantoin likely becomes accessible to these degradative enzymes . Because they are already present at high levels, the fact that their inducer is considerably removed from the input allantoin is of little consequence . This suggests that at times metabolite compartmentation may play an equal role with enzyme induction in the regulation of allantoin metabolism . Metabolism of arginine, another sequestered metabolite, must be controlled both by induction of arginase and compartmentation because arginine serves both as a reserve nitrogen source and a precursor of protein synthesis . The latter function precludes the existence of high basal levels of arginase.

Cell, 1978 Aug, 14(4), 951 - 8
RNA synthesis and control of cell division in the yeast S . cerevisiae; Johnston GC et al.; Cells of the yeast Saccharomyces cerevisiae rapidly accumulated in the G1 phase of the cell cycle when exposed to the chelating agents o-phenanthroline (OP) or 8-hydroxyquinoline (HQ) . Zinc salts fully reversed the growth-inhibitory effect of both OP and HQ . Cells treated with these chelating agents showed limited RNA accumulation and little RNA degradation . Rates of RNA synthesis were drastically reduced by low concentrations of these compounds . Whereas rates of protein synthesis were essentially unaffected . Rates of synthesis of mRNA and tRNA were less affected than were rates of synthesis of high molecular weight RNA . Processing of ribosomal precursor RNA was altered . these results suggest that the primary effect of OP and HQ is on rRNA synthesis . RNA metabolism must therefore have a key role in the regulation of the cell cycle.

Mol Gen Genet, 1978 Jun 14, 162(2), 173 - 82
Fidelity of conjugation in Saccharomyces cerevisiae; Rogers D et al.; An efficient method for the production of synchronous zygotes in Saccharomyces cerevisiae is described . Cells were synchronised under defined conditions in either an a, alpha mixed culture or by incubation of each mating type in cell-free medium in which cells of the opposite mating type had been grown . Synchronised cells were allowed to fuse under defined conditions on filter membranes . This method was used to test the fidelity of conjugation in S . cerevisiae . Under conditions where cells of a or alpha mating type were in contact with up to 6 cells of each of two strains of opposite mating type, less than 1 multiple mating in 10(4) diploid matings occurred . It is concluded that is sexual conjugation in S . cerevisiae some process distinct from cell contact restricts cell fusion to paired combinations of conjugant cells.

Immunology, 1978 Apr, 34(4), 689 - 94
A new semiquantitative radiometric opsonin assay . Selective measurement of opsonizing capacity of the alternative pathway; Yamamura M et al.; A new semiquantitative radiometric opsonin assay is described . It was found that the opsonin activity generated by incubating brewer's yeast, Saccharomyces cerevisiae, in medium containing less than 5% human serum was exclusively complement dependent . In contrast, C . albicans was effectively opsonized in the absence of complement . Antibodies and the early classical complement pathway did not contribute to the opsonization of S . cerevisiae and neither did C5-9 . The brewer's yeast assay can therefore be used for measuring selectively the opsonizing capacity of the alternative pathway . Sera from approximately 7% of apparently healthy adult controls consistently failed to generate significant opsonin activity while 8 out of 26 patients with suspected immune deficiency of unknown cause were defective in this assay . All opsonin deficient sera so far tested had haemolytically normal alternative pathway and Factor B activity.

Genetics, 1978 Apr, 88(4 Pt 1), 673 - 87
Gene duplication in Saccharomyces cerevisiae; Hansche PE et al.; Five independent duplications of the acid-phosphatase (aphtase) structural gene (acp1) were recovered from chemostat populations of S . cerevisiae that were subject to selection for in vivo hyper-aphtase activity . Two of the duplications arose spontaneously . Three of them were induced by UV . All five of the duplication events involved the transpositioning of the aphtase structural gene, acp1, and all known genes distal to acp1 on the right arm of chromosome II, to the terminus of an arm of other unknown chromosomes . One of the five duplicated regions of the right arm of chromosome II was found to be transmitted mitotically and meiotically with very high fidelity . The other four duplicated regions of the right arm of chromosome II were found to be unstable, being lost at a rate of about 2% per mitosis . However, selection for increased fidelity of mitotic transmission was effective in one of these strains . No tandem duplications of the aphtase structural gene were found.

Mutat Res, 1978 Mar, 49(3), 371 - 6
Effects of the epoxide hydrase inhibitor, 1,1,1-trichloropropane-2,3-oxide on the genetic activity of aflatoxin B1 metabolites in in vitro activation test systems; Callen DF et al.; The epoxide hydrase inhibitor 1,1,1-trichloroprophane-2,3-oxide (TCPO) was genetically active to cells of S . cerevisiae and conidia of N . crassa . This genetic activity could be eliminated or reduced to near spontaneous levels in the presence of the S-9 fraction of hamster liver homogenate . The addition of TCPO to an in vitro activation system containing aflatoxin B1 resulted in an increase in the genetic activity of aflatoxin B1, and this increase was dependent on the dose of TCPO . These results are discussed in relation to the possible metabolism of the promutagen aflatoxin B1.

Antonie Van Leeuwenhoek, 1978, 44(3-4), 341 - 52
Inositol deficiency in yeast: metabolic, enzymatic and autoradiographic studies; Dominguez A et al.; The addition of inositol to starved cells of Saccharomyces cerevisiae NCYC 86 resulted in an initiation of growth . Inositol was incorporated into phosphatidyl-inositol and after a lag period RNA was the first macromolecule with a rate of synthesis departing from the rate observed in deprived cells . Pulse chase experiments showed that inositol was first incorporated into phosphatidylinositol and later into more polar lipids . Finally it appeared to be excreted into the surrounding medium . When S . cerevisiae NCYC 86 was grown in suboptimal concentrations of inositol (0,5 microgram/ml), alterations in the level of some membrane-bound enzymatic activities were detected; these might reflect structural modifications of the cellular membranes due to a different composition of phospholipids . High-resolution autoradiography showed that inositol was probably first incorporated into internal membranes and later transferred to the plasma membrane . Analytical experiments carried out with inositol-deprived cells showed that inositol was released into the surrounding medium in that case . The unbalanced growth detected in S . cerevisiae NCYC 86 under inositol deprivation might be due to an abnormal functioning of the cell membranes as a consequence of the deficiency in inositol-containing phospholipids.

Genetics, 1978 Jan, 88(1), 1 - 11
Glycolysis mutants in Saccharomyces cerevisiae; Clifton D et al.; Mutants have been isolated in S . cerevisiae with the phenotype of growth on pyruvate but not on glucose, or growth on rich medium with pyruvate but inhibition by glucose . Screening of mutagenized cultures was either without an enrichment step, or after enrichment using the antibiotic netropsin (Young et al . 1976) or inositol starvation (Henry, Donahue and Culbertson 1975) . One class of mutants lacked pyruvate kinase (pyk), another class had all the enzymes of glycolysis, and one mutant lacked phosphoglucose isomerase (pgi, Maitra 1971) . Partial reversion of pyruvate kinase mutants on rich medium containing glucose gave double mutants now also lacking hexokinase (hxk), phosphofructokinase (fk), or several enzymes of glycolysis (gcr) . In diploids the mutations were recessive . pyk, pgi, pfk, and gcr segregated 2:2 from their wild-type alleles . PYK hxk, PYK pfk, and PYK gcr segregrants grew on glucose.

Can J Microbiol, 1977 Dec, 23(12), 1669 - 74
L-methionine as an ethylene precursor in Saccharomyces cerevisiae; Thomas KC et al.; L-Methionine induced production of ethylene by Saccharomyces cerevisiae growing in lactate medium . The production induced by L-methionine was inhibited by pyruvate, and elevated by glucose . Labeled ethylene was produced when L-{U-14C}methionine, but not {U-14C}glucose, was fed to the yeast . The mutant S . cerevisiae G1332 (ade-, met-) did not produce significant amounts of ethylene unless L-methionine was added . Thus L-methionine acts as a precursor of ethylene in S . cerevisiae . The role of glucose appears to be other than as a precursor.

J Cell Biol, 1977 Nov, 75(2 Pt 1), 422 - 35
Unequal division in Saccharomyces cerevisiae and its implications for the control of cell division; Hartwell LH et al.; The budding yeast, Saccharomyces cerevisiae, was grown exponentially at different rates in the presence of growth rate-limiting concentrations of a protein synthesis inhibitor, cycloheximide . The volumes of the parent cell and the bud were determined as were the intervals of the cell cycle devoted to the unbudded and budded periods . We found that S . cerevisiae cells divide unequally . The daughter cell (the cell produced at division by the bud of the previous cycle) is smaller and has a longer subsequent cell cycle than the parent cell which produced it . During the budded period most of the volume increase occurs in the bud and very little in the parent cell, while during the unbudded period both the daughter and the parent cell increase significantly in volume . The length of the budded interval of the cell cycle varies little as a function of population doubling time; the unbudded interval of the parent cell varies moderately; and the unbudded interval for the daughter cell varies greatly (in the latter case an increase of 100 min in population doubling time results in an increase of 124 min in the daughter cell's unbudded interval) . All of the increase in the unbudded period occurs in that interval of G1 that precedes the point of cell cycle arrest by the S . cerevisiae alpha-mating factor . These results are qualitatively consistent with and support the model for the coordination of growth and division (Johnston, G . C., J . R . Pringle, and L . H . Hartwell . 1977 . Exp . Cell . Res . 105:79-98.) This model states that growth and not the events of the DNA division cycle are rate limiting for cellular proliferation and that the attainment of a critical cell size is a necessary prerequisite for the "start" event in the DNA-division cycle, the event that requires the cdc 28 gene product, is inhibited by mating factor and results in duplication of the spindle pole body.

J Bacteriol, 1977 Sep, 131(3), 906 - 16
Peptide transport in yeast: utilization of leucine- and lysine-containing peptides by Saccharomyces cerevisiae; Marder R et al.; A variety of leucine-containing di- and tripeptides and two lysine-containing dipeptides supported the growth of strain Z1-2D, a leucine, lysine auxotroph of Saccharomyces cerevisiae . However, (Lys)2, (Lys)3, (Lys)4, and (Lys)5 as well as Gly-Leu-Gly, three tetra- and one pentapeptide containing leucine were not utilized by the mutant . Cellular peptidases released leucine or lysine from all of these non-growth-supporting peptides, suggesting that the failure of strain Z1-2D to utilize these compounds reflects their failure to enter the yeast . Competition studies employing phenylalanine or non-leucine-containing peptides showed that the uptake of peptides into S . cerevisiae Z1-2D is distinct from that of amino acids and that di- and oligopeptides may share a common transport system . The failure of strain Z1-2D to utilize any peptide larger than (Leu)3 may indicate a transport size limit . Such a size limit would influence the construction of models that explain the action of yeast mating factors.

Mutat Res, 1977 Aug, 44(2), 217 - 26
Dynamics of x-ray-induced reversion in heterogeneous S . cerevisiae populations; Eklund T; The survival and frequency of adenine and homoserine revertants after X-irradiation have been studied in starved and growing populations of haploid S . cerevisiae (strain 5483/1b) . A growing population is heterogeneous to cell killing, and a mathematical model can be used to determine possible correlation between sensitivity to killing and sensitivity to mutation induction . The results indicate correlation between sensitivity to ade2-1 reversion and sensitivity to cell killing, whereas no such correlation was found between sensitivity to hom3-10 reversion and sensitivity to killing . The difference in the dynamics of homoserine and adenine reversions was reduced by adding caffeine to the post-irradiation media.

Nucleic Acids Res, 1977 Jul, 4(7), 2331 - 51
Restriction cleavage map of mitochonrial DNA from the yeast Saccharomyces cerevisiae; Morimoto R et al.; Mitochondrial DNA (mtDNA) from the yeast Saccharomyces cerevisiae was cleaved by restriction endonucleases Eco RI, Hpa I, Bam HI, Hind III, Pst I, and Sal I, yielding 10, 7, 5, 6, 1, and 1 fragments, respectively . A physical ordering of the restriction sites on yeast mtDNA has been derived . Yeast mtDNA cannot be isolated as intact molecules, and it contains nicks and gaps which complicate the use of conventional fragment mapping procedures . Nevertheless, the position of each of the restriction sites was obtained primarily by reciprocal redigestion of isolated restriction fragments . This procedure was supplemented by co-digestion of mtDNA with a multisite enzyme and a single-site enzyme (i.e., Sal I or Pst I) which provided a unique orientation for overlapping fragments cleaved by Sal I or Pst I . The data obtained from these approaches were confirmed by analysis of double and triple enzyme digests . Analysis of partial digest fragments was used for positioning of the smallest Eco RI fragment . A comparison of mtDNA from four grande strains (MH41-7B, 19d, TR3-15A, and MH32-12D) revealed similar, but slightly varying restriction patterns, with an identical genome size for each of approximately 5 X 10(-7) d or 75 kb . A fifth grande strain, D273-10B from S . cerevisiae, revealed restriction patterns different from those of the above strains, with a smaller genome size of 70 kb.

J Cell Sci, 1977 Apr, 24, 81 - 93
Chromatin behaviour during the mitotic cell cycle of Saccharomyces cerevisiae; Gordon CN; Chromatin behaviour during the cell division cycle of the yeast Saccharomyces cerevisiae has been investigated in cells which have been depleted of 90% of their RNA by digestion with ribonuclease . Removal of large amounts of RNA from the yeast nucleus before treatment of the cells with heavy metal fixatives and stains permits chromatin to be visualized with extreme clarity in thin sections of cells processed for electron microscopy by conventional procedures . Spindle pole bodies were also visualized by this treatment, although the associated microtubules were not . Chromatin is dispersed during interphase and occupies the non-nucleolar region of the nucleus which is known to be Feulgen-positive from light microscopy . Because spindle microtubules are not visualized, direct attachment of microtubules to chromatin fibrils could not be verified . However, chromatin was not attached directly to the spindle pole bodies and kinetochore differentiations were not observed in the nucleoplasm . During nuclear division chromatin remains dispersed and does not condense into discrete chromatids . As the nucleus expands into the bud, chromosomal distribution to the daughter cells is thought to result from the separation of the poles of the spindle apparatus with attached chromatin fibrils . However, that such distribution is occurring as the nucleus elongates is not obvious until an advanced stage of nuclear division is reached and partition of the nucleus is nearly complete . Thus, no aggregation of chromatin into metaphase or anaphase plates occurs and the appearance of chromatin during mitosis is essentially the same as in interphase . These observations indicate that the marked changes in the topological structure of chromatin which characterize mitosis in the higher eukaryotes do not occur in S . cerevisiae.

J Antibiot (Tokyo), 1977 Apr, 30(4), 308 - 13
On the mode of action of a new antifungal antibiotic, aculeacin A: inhibition of cell wall synthesis in Saccharomyces cerevisiae; Mizoguchi J et al.; The mode of action of a new antifungal antibiotic, aculeacin A, was studied with the cells of Saccharomyces cerevisiae . In the presence of aculeacin A, the distinct decrease of viable cells was observed . The most of cells treated with aculeacin A lysed with releasing intracellular substances at the tips of their buds . This lysis was considered to be due to the inhibition of cell wall synthesis, because the incorporation of glucose into the cell wall glucan was significantly reduced . Aculeacin A also had a weak activity to burst the protoplasts of S . cerevisiae at a relatively high concentration.

J Bacteriol, 1977 Apr, 130(1), 11 - 9
Methionyl-transfer ribonucleic acid deficiency during G1 arrest of Saccharomyces cerevisiae; Unger MW; The mesl- mutants of Saccharomyces cerevisiae cease division and accumulate in the G1 interval of the cell cycle when deprived of methionine or shifted from 23 to 36 degrees C in the presence of methionine . Synchronous cell cycle arrest results from a deficiency of charged methionyl-transfer ribonucleic acid (methionyl-tRNAMet) as shown by direct measurement of the in vivo pools of methionine, S-adenosylmethionine, and methionyl-tRNAMet . The deficiency of methionyl-tRNAMet in these cells is the consequence of a lesion in a single gene, mes1 . mes1 appears to be the structural gene for the methionyl-tRNA synthetase because some revertants of this mutation exhibited a thermolabile methionyl-tRNA synthetase in vitro . A sufficient hypothesis to explain these and previous results is that the control of cell division by S . cerevisiae in response to nutrient limitation is mediated through aminoacyl-tRNA or subsequent steps in protein biosynthesis.

Biotechnol Bioeng, 1977 Feb, 19(2), 267 - 96
A mechanistic model of the aerobic growth of Saccharomyces cerevisiae; Bijkerk AH et al.; A two-stage deterministic model of the growth of Saccharomyces cerevisiae is presented . The cell cycle of this organism was used to suggest the basic model structure . The model represents the preparatory processes of substrate uptake and conversion separately from replication and division . The regulation of the fraction of the culture devoted to each of these broad areas of metabolism, and the overall growth rate, is related to the nature and availability of the energy substrate . The simulation of respiration and glycolysis is achieved by including two alternative energy producing pathways . The regulation of these pathways is described in terms of the postulated primary regulation of the proportion of the culture required for substrate uptake and conversion, and the overall kinetic constants for each pathway . This regulation is dictated primarily by the growth rate rather than the nature or concentration of the energy substrate . The model successfully describes both batch and continuous growth of S . cerevisiae under conditons of glucose limitation and oxygen excess . A preliminary assessment indicates that adjustment of the relevant parameters will allow the model to describe the growth of S . cerevisiae on other sugars and under oxygen limitation . Similarly the model could be expected to describe the growth characteristics of other yeast species.

J Bacteriol, 1977 Feb, 129(2), 978 - 82
Gluconeogenesis in Saccharomyces cerevisiae: determination of fructose-1,6-bisphosphatase activity in cells grown in the presence of glycolytic carbon sources; Foy JJ et al.; The activity of fructose-1,6-bisphosphatase (FBP), a gluconeogenic enzyme, was determined in wild-type Saccharomyces cerevisiae X2180 grown in the presence of the glycolytic carbon sources, glucose, fructose, and galactose . The activities of phosphofructokinase (PFK), a glycolytic enzyme, and phosphoglucose isomerase (PGI), an enzyme functioning both in glycolysis and gluconeogenesis, were determined for purposes of comparison . A measurable amount of FBP activity was present in 20-h-old cells grown with moderate shaking in 1% glucose-nutrient or minimal medium . This activity increased significantly in 40 and 60-h-old cells . Similar levels of FBP activity were also present in 20-, 40-, and 60-h-old cells grown in 1% fructose-nutrient medium . A higher level of FBP activity was present in 20-h-old cells grown in 1% galactose-nutrient medium than in 20-h-old cells grown in 1% glucose- or fructose-nutrient medium . The FBP activity in glucose- or fructose-grown cells was higher than the corresponding activity in cells grown under similar conditions for 40 and 60 h in the presence of ethanol, a gluconeogenic carbon source . The PFK activity was significantly less in galactose- and ethanol-grown cells . The PGI activity was relatively constant in 20-, 40-, and 60-h-old cells grown in the presence of glucose, fructose, and galactose, but this activity was reduced approximately 50% in ethanol-grown cells . It is concluded from these results that, depending upon the concentration of carbon source and the time of incubation, FBP, a strictly gloconeogenic enzyme, is synthesized by S . cerevisiae grown in the presence of glycolytic carbon sources.

Zentralbl Bakteriol Parasitenkd Infektionskr Hyg, 1977, 132(7), 641 - 7
Studies on protein production by yeasts . III . Effects of different levels of nitrogen and phosphorus; El-Sawy M et al.; The four strains of yeasts that gave good growth in molasses medium, short generation time, and high protein content were selected for further studies in a trial for increasing their yield and protein content . Therefore, the effect of different levels of ammonium sulphate and potassium dihydrogen phosphate on the growth and protein synthesis of the strains was investigated, using molasses as a source of carbon . The results revealed that the most suitable concentrations of ammonium sulphate in the propagation medium lie between 0.40 to 0.55% for the production of high yield and protein content of strains S . cerevisiae (Gr . 104), C . utilis (F . 86), C . tropicalis (F . 35), and H . anomala (Gr . 5) . The optimum concentration of potassium dihydrogen phosphate lies between 0.2 to 0.3% for the same strains . S . cerevisiae (Gr . 104) seemed to be the most efficient strain that gave the best growth, high percentage of protein, and essential amino acids in molasses medium.

Genetics, 1977 Jan, 85(1), 23 - 33
Proteinase mutants of Saccharomyces cerevisiae; Jones EW; Fifty-nine mutants with reduced ability to cleave the chymotrypsin substrate N-acetyl-DL-phenylalanine beta-naphthyl ester have been isolated in S . cerevisiae . All have reduced levels of one or more of the three well-characterized proteinases in yeast . All have reduced levels of proteinase C (carboxy-peptidase Y) . These mutations define 16 complementation groups.

J Mol Evol, 1976 Dec 31, 9(1), 25 - 35
Organization and evolution of the mitochondrial genome of yeast; Bernardi G; The mitochondrial genome of yeast (S . cerevisiae or S . carlsbergensis) appears to be formed by 60-70 genetic units, each one of which is formed by (1) a GC-rich sequence, possibly having a regulatory role; (2) a gene, and (3) an AT-rich spacer, which probably is not transcribed . Recombination in this genome appears to underlie a number of important phenomena . The organization of the mitochondrial genome of yeast and these recombinational events are discussed in relationship with the organization and evolution of the nuclear genome of eukaryotes.

Proc Natl Acad Sci U S A, 1976 Dec, 73(12), 4608 - 12
Modified recombination and transmission of mitochondrial genetic markers in rho minus mutants of Saccharomyces cerevisiae; Boltin-Fukuhara M et al.; A large number of primary petite (rho-) clones were isolated after ethidium bromide mutagenesis of various grande (rho+) strains of S . cerevisiae that contained the mitochondrial genetic markers, CR, ER, OIR (or OIIR), and PR . From the frequency of coretention of markers in the petites, we have deduced a probable circular order of the markers in the grande mitochondrial genome . From these primary clones several series of pure and stable petite clones were obtained and analyzed genetically . (a) In general, the omega allele is retained or lost together with the region carrying both CR and ER markers . (b) The petites that have retained only the CR marker fall into two classes: some have kept the omega allele of the grande strain they issued from; others exhibit a new omega expression . (c) The proportion of diploid petites in petite X grande crosses is independent of the presence of the omega allele . (d) In most cases, the coordinated transmission of markers observed so far in all grande X grande nonpolar corsses does not exist anymore in petites.

Biochim Biophys Acta, 1976 Dec 1, 454(2), 263 - 72
Cell wall synthesis regulation in Saccharomyces cerevisiae . Effect of RNA and protein inhibition; Elorza MV et al.; In this investigation the regulation of wall formation in Saccharomyces cerevisiae ts-136 (Hutchison, H.T., Hartwell, L.H . and McLaughlin, C.S . (1969) J . Bacteriol . 99, 807-814) was analyzed by following the inhibition of RNA and protein synthesis . Lomofungin, thiolutin and 8-hydroxyquinoline at the concentrations needed to inhibit RNA synthesis also produced inhibition of glucan and mannan synthetases . The synthesis of RNA was also blocked in S . cerevisiae ts-136 by incubation at the non-permissive temperature (37 degrees C) . Mannan formation decreased steadily but glucan synthesis remained after 4 to 5 h . After a few minutes of blocking protein synthesis with cycloheximide mannan synthesis was also blocked whereas glucan formation was unaffected by the presence of the drug . These results suggest a high degree of stability for glucan synthetases . S . cerevisiae ts-136 after 2 h of incubation at the non-permissive temperature (37 degrees C) showed a preferential formation of wall materials (mannan and glucan) indicating that the RNA messengers which codify wall mannan peptides have a slower decay rate than those of the cytoplasmic proteins . The data presented indicate that the existence of stable glucan synthetases and RNA messengers of the wall mannan peptides of slow decay rate results in the continuous synthesis of glucans and mannoproteins of the yeast wall throughout the cell cycle.

Mol Gen Genet, 1976 Nov 24, 149(1), 43 - 50
Assembly of the mitochondrial membrane system . XIX . Genetic characterization of mit- mutants with deficiencies in cytochrome oxidase and coenzyme qh2-cytochrome c reductase; Foury F et al.; Nineteen mutants of S . cerevisiae exhibiting a double deficiency in cytochrome oxidase and coenzyme QH2-cytochrome c reductase (also cytochrome b deficient) have been studied . The mutants have been crossed to a set of rho- tester strains with different segments of mitochondrial DNA . The mutants have also been crossed to mit- testers with defined genetic lesions . In addition, crosses were performed with a respiratory competent strain to ascertain whether mitotic and meiotic segregants could be isolated with only one of the two enzymatic deficiencies . The rho- testers allowed the doubly deficient mutants to be separated into two classes . Mutants in class 1 were not restored by any of the rho- testers and appeared to have separate mutations, one in cytochrome oxidase and the other in cytochrome b . Mutants in class 2 were restored by a set of rho- clones whose retained segments of mitochondrial DNA contained the cytochrome b but not the cytochrome oxidase loci . These appeared to behave as single hit mutations . Further studies, however, indicated that both class 1 and class 2 mutants carried separate mutations in two different loci . Mitotic and meiotic segregants with a single enzymatic deficiency could be isolated . In a number of strains, the mutations were mapped in known cytochrome oxidase and cytochrome b loci . The apparent discrepancy of the rho- tests for the class 2 mutants was shown to be probably due to a high unstability in one of the mutations . It has been concluded that all the doubly deficient strains carry two mutations in previously described cytochrome oxidase and cytochrome b loci . This conclusion argues against the existence of a single gene on mitochondrial DNA that controls the biosynthesis of the two respiratory enzymes.

Mol Gen Genet, 1976 Nov 17, 148(3), 287 - 94
A map of the restriction targets in yeast 2 micron plasmid DNA cloned on bacteriophage lambda; Beggs JD et al.; The 2 micron circular DNA from S . cerevisiae has been cloned on bacteriophage lambda . The two forms of circular DNA which exist in equilibrium due to recombination between inverted repeat sequences were separated as stable clones, and a map of targets for restriction endonucleases EcoRI, HindIII and HpaI was constructed . The circular DNAs isolated from a particular oligomycin resistant strain and its parent oligomycin snesitive strain were compared by restriction endonuclease analysis, and no difference was detected . The potential uses of cloned 2 micron DNA in determining the possible biological role of these plasmids are considered.

J Biochem (Tokyo), 1976 Nov, 80(5), 951 - 9
The primary structure of non-initiator methionine transfer ribonucleic acid from Bakers' yeast . II . Partial digestion with ribonuclease T1 and derivation of the complete sequence; Koiwai O et al.; Large oligonucleotides obtained from partial RNase T1 digestion of tRNAMetm from bakers' yeast (S . cerevisiae, strain Y 185) were isolated by chromatographic procedures and sequenced . The complete sequence of the tRNAMetm was established from the results of this partial digestion, together with those of the complete RNase T1 and A {EC 3.1.4.8 and 22} digestions of tRNAMetm reported in the preceding paper . The structure of this tRNAMetm was arranged into a clover leaf comparable with those of other tRNAMet species including bakers' yeast initiator tRNA.

Eur J Biochem, 1976 Nov 1, 70(1), 75 - 81
Interaction of concanavalin A with external mannan-proteins of Saccharomyces cerevisiae . Glycoprotein nature of beta-glucanases; Biely P et al.; beta-Glucanases secreted into culture fluid by protoplasts or intact cells of the yeast Saccharomyces cerevisiae were investigated for the presence of covalently linked carbohydrates . Gel filtration of the enzymes on Biogel A-1.5m showed that endo-beta-1,3-glucanase is a polydisperse enzyme of high-molecular weight which elutes in about the same volume as external yeast invertase . Exo-beta-glucanase was eluted from the gel as a much lighter enzyme . Endo-beta-1,3-glucanase added to a mixture of extracellular mannoproteins was precipitated by concanavalin A to a similar extent to mannan, invertase and acid phosphatase . Under the same conditions exo-beta-glucanase did not interact with the lectin, but was partially precipitated from the solution in the absence of foreign mannan or mannan-proteins . The results show that endo-beta-1,3-glucanase of S . cerevisiae is a mannoprotein of a similar nature to external invertase and acid phosphatase . However, exo-beta-glucanase appears to be a glycoprotein which does not contain the highly branched mannan polymer in its molecule.

Mol Gen Genet, 1976 Oct 18, 148(1), 65 - 77
Effect of auxotrophic starvation of mitochondrial marker transmission in the cdc8 mutant of Saccharomyces cerevisiae; Kruszewska A et al.; Crosses were made using strains of S . cerevisiae which carried mitochondrial markers conferring resistance to erythromycin and chloramphenicol . The effect of auxotrophic starvation of one parent prior to mating on the transmission of its mitochondrial markers was studied in different crosses relative to the presence of the cdc8 nuclear mutation (a temperature-sensitive DNA replication) . In crosses between two cdc8 mutant strains, auxotrophic starvation of one of the haploid parental stains prior to mating caused a marked decrease of its mitochondrial marker transmission to the diploid progeny of the cross . The transmission decreased as a function of the time of starvation . This effect was not observed in the cross between two wild type strains and in crosses of starved cdc8 phenotypic revertants with cdc8 mutant strains . Only a small, if any, effect of starvation on mitochondrial marker transmission was observed when starved cdc8 mutant strains were crossed either with their phenotypic revertants or with the wild-type strains . In one of the haploid parental strains the starvation increased the frequency of petites as a function of starvation time, while in the other this effect was not observed . In the progeny of cdc8 X cdc8 crosses (both in starvation experiments and in control crosses) an increased frequency of diploid petite cells accompanied by a decreased frequency of recombination between mitochondrial markers was noticed . The influence of the cdc8 mutation on the transmission of mitochondrial markers is discussed in terms of high frequency of p- molecule formation in cdc8 strains.

Biokhimiia, 1976 Oct, 41(10), 1878 - 88
{Lability of the products of mitochondrial protein synthesis in Saccharomyces cerevisiae yeasts}; Bakalkin GI et al.; Estimation of the rate of degradation of the products of mitochondrial protein synthesis in S . cerevisiae cells is reported . The method developed for this purpose is based on pulse incorporation of a labeled amino acid in the presence of an inhibitor of cytoplasmic protein synthesis and allows one to monitor postincorporation of the label . The label incorporated is shown to be rapidly released from mitochondria . Its content is decreased 2-fold during 20-30 min at the beginning and 50-60 min at the end of the exponential phase of growth . The label is detected in cytosol proteins and the TCA-soluble fraction of mitochondria, which is indicative of possible proteolysis of mitochondrial membrane proteins . Since release of the label does not undergo inhibition by specific inhibitors of yeast cell proteinases (pepstatin and phenylmethylsulfonyl fluoride), it may be assumed that these proteinases are either not involved in the digestion of the products of mitochondrial protein synthesis or do not represent a rate-limiting step of the process.

Z Naturforsch {C}, 1976 Sep-Oct, 31(9-10), 509 - 13
{O-Methylation of epinephrine, 3,4-dihydroxybenzoic acid and 6,7-dihydroxycoumarin in yeasts (author's transl)}; Muller-Enoch D et al.; In the yeasts C . albicans, C . tropicalis, and C . stellatoidea but not in C . krusei, R.rubra, and S . cerevisiae enzyme activity was found by which--as by the catechol-O-methyltransferase (EC 2.1.1.6) found in the liver--the O-methylation of epinephrine to metanephrine and paranephrine, of 3,4-dihydroxybenzoic acid to 4-hydroxy-3-methoxybenzoic acid and 3-hydroxy-4-methoxybenzoic acid, and of 6,7-dihydroxycoumarin to 7-hydroxy-6-methoxycoumarin and 6-hydroxy-7-methoxycoumarin is catalysed . When the substrates 3,4-dihydroxybenzoic acid, or 6,7-dihydroxycoumarin or epinephrine were incubated in the presence of S-adenosyl-L-{methyl-14C}methionine and S-adenosylmethionine hydrogensulfate with a 100 000 X g supernatant of C . albicans, C . tropicalis or C . stellatoidea the corresponding O-methylethers were detected in the extracts of the incubation medium by thin-layer chromatography . Final identification of the isomeric radioactive O-methylethers obtained from 3,4-dihydroxybenzoic acid and 6,7-dihydroxycoumarin was performed after thin-layer chromatographic separation by the reversed isotope dilution technique . The radioactive m- and p-O-methyl derivatives from epinephrine were separated by thin-layer chromatography and then cleaved with periodate to the corresponding aldehydes which were also identified mainly by the reversed isotope dilution technique.

Mol Gen Genet, 1976 Aug 19, 147(2), 153 - 68
Characterization of yeast ribosomal DNA fragments generated by EcoR1 restriction endonuclease; Nath K et al.; The action of Escherichia coli restriction endonuclease R1 (EcoR1) on DNA isolated from Saccharomyces cerevisiae (strain MAR-33) generates three predominent homogenously sized DNA fragments (species of 1.8, 2.2 and 2.5 kilo nucleotide base pairs (KB) . Many DNA species of molecular weight greater than 2 million daltons can be recognized upon incomplete EcoR1 digestion of yeast DNA . Four additional DNA species ranging from 0.3--0.9 KB can be identified as the second major class of EcoR1-yeast DNA products . Hybridization with radioactive ribosomal RNA (rRNA) and competition with nonradioactive rRNA show that of the three predominent EcoR1-yeast DNA species, the 2.5 KB species hybridizes only with the 25S rRNA while the lighter 1.8 KB species hybridizes with the 18S rRNA . The intermediate DNA species of 2.2 KB hybridizes to a small extent with the 25S rRNA and could be a result of the presence of the 2.5 KB DNA species . The mass proportions and hybridization values of these 3 DNA species account for about 60% of the total ribosomal DNA (rDNA) . The 5 Eco-R1-yeast DNA species of less than 0.9 KB (4 major and 1 minor species) hybridize to varying degrees with the 2 rRNA and can be grouped in two classes . In one class there are 3 DNA species that hybridize exclusively with the 18S rRNA . In the second class there are 2 DNA species that besides hybridizing predominently with the 25S rRNA also hybridize with the 18S rRNA . The 7 EcoR1-yeast DNA species (excluding the 2.2 KB DNA species) that hybridize with the two rRNA account for nearly a 5 million dalton DNA segment, which is very close to the anticipated gene size of rRNA precursor molecule . If the 2.2 KB DNA species is a part of the rDNA that is not transcribed or 5 sRNA then the cistron encoding the rRNA in S . cerevisiae has at least 8 EcoR1 recognition sites resulting in 8 DNA fragments upon digestion with the EcoR1 . Consideration is given to the relationship of the rRNA species generated by EcoR1 digestion and the chromosomes containing ribosomal cistrons.

Ann Microbiol (Paris), 1976 Aug-Sep, 127B(2), 151 - 66
{The inhibition of post-exponential growth in "Saccharomyces cerevisiae" by L-lysine (author's transl)}; Bourgeois CM; The inhibitory effect of L-lysine upon the post-exponential growth of Saccharomyces cerevisiae has been previously demonstrated and the present report extends the observation . During the post exponential phase, the cells do not divide but the cell mass normally increases two or three-fold; in the presence of exogenous lysine this increase is considerably reduced, bud growth is blocked and the cytological features of the post-exponential cells are considerably modified . The effect is apparent in liquid as well as on solid media . L-alpha-aminoadipate, being a precursor of L-lysine, exerts a similar effect since the exponential phase . Mutants resistant to the effect of lysine proved to be permeability mutants . The phenomenon is not restricted to any one strain of S . cerevisiae but characterized all strains of the species which are unable to catabolize lysine.

Arch Microbiol, 1976 Aug, 109(1-2), 9 - 14
Localization of mannan at the surface of yeast protoplasts by scanning electron microscopy; Horisberger M et al.; The beta(1-3)glucanase of Basidiomycete QM 806 was used to prepare Saccharomyces cerevisiae and Candida utilis protoplasts . Plasma membranes isolated from S . cerevisiae contained a small amount of mannose and traces of glucose and ribose . Randomly distributed alpha-mannan was detected by scanning electron microscopy at the surface of prefixed protoplasts using colloidal gold labelled with Concanavalin A as a marker . C . utilis protoplasts were also marked with anti-mannan antibodies . Again the distribution of mannan was random . This experiment indicated also that plasma membrane mannan has the same immunochemical determinants as cell wall mannan . It is hypothesized that mannan is mainly located in the outer layer of plasma membranes.

Mol Biol (Mosk), 1976 Jul-Aug, 10(4), 767 - 71
Double-stranded RNA of homothallic Saccharomycetes with different cytoplasmic determinants of antagonistic activity; Nesterova GF et al.; Double-stranded RNA of high molecular weight is found in the cytoplasm of the "killer" strain M-437-2 . The RNA is homogeneous and contains no single strand poly(A) portions . The double-stranded RNA is associated with the cytoplasmic microsomes of strain M-437-2 and is contained in the fraction of the cell contents of this strain that was used to infect germinating spores of the sensitive S . cerevisiae 768(1)-15 with the cytoplasmic determinant {k} . The absence of this RNA in cells of the initial sensitive strain 768(1)-15, and its appearance in the "killer" derivative of this strain produced by infection with the determinant {k} by means of the above-mentioned fraction, indicate that the killer activity is due to the double-stranded RNA . The retention of the double-stranded RNA in the cytoplasm of derivatives of the newly-formed killer strain, containing the cytoplasmic determinants {k(ts)} and {n} suggests also that these determinants are a modification of determinant {k}.

Can J Biochem, 1976 Jul, 54(7), 657 - 65
The induced biosynthesis of 7-dehydrocholesterols in yeast: potential sources of new provitamin D3 analogs; Avruch L et al.; The effect of low concentrations of a specifically designed sterol-24-transmethylase inhibitor, 25-aza-24, 25-dihydrozymosterol (10) on sterol production in Saccharomyces cerevisiae was examined . The synthesis of cholesta-5,7,22,24-tetraen-3beta-ol (4), its 7,22,24 analog (15) and the 7,24 analog (5) coupled with the availability of zymosterol (6) and cholesta-5,7,24-3beta-ol (3) derivatives facilitated a search for these sterols in cultures treated with this inhibitor . When S . cerevisiae was grown in the presence of 1.3 and 5 muM 10, it produced no ergosterol but accumulated zymosterol (6), cholesta-5,7,22,24-tetraen-3beta-ol (4) and related C27 sterols (3 and 5) . These results indicate blockage of the side chain methylation that normally occurs during the biosynthesis of ergosterol in yeast by compound 10 is efficient . The cholesta-5,7,22,24-tetraen-3beta-ol is a close structural analog of provitamin D3 (7-dehydrocholesterol) . The inhibited yeast thus provides a source of a potentially new provitamin D3 substitute.

Biochemistry, 1976 Jun 1, 15(11), 2289 - 96
In vivo and in vitro phosphorylation of ribosomal proteins by protein kinases from Saccharomyces cerevisiae; Becker-Ursic D et al.; From the high salt wash of the ribosomes of the yeast Saccharomyces cerevisiae, three protein kinases have been isolated and separated by DEAE-cellulose chromatography . The three kinases differ in their abilities to phosphorylate substrates such as histones (calf thymus), casein, and S . cerevisiae ribosomes; two of the kinases showed increased activity in the presence of cyclic adenosine 3',5'-monophosphate when histones and 40S ribosomal subunits were used as substrates . The protein kinases catalyzed phosphorylation of certain proteins of the 40S and 60S ribosomal subunits, and 80S ribosomes in vitro . Nine proteins of the 80S ribosome, seven proteins of the 40S subunit, and eleven of the 60S subunit were phosphorylated; different proteins were modified to various extents when different kinases were used . We have identified several proteins of 40S and 60S ribosomal subunits which are not available to the kinases in the 80S particles . Ribosomes isolated from S . cerevisiae cells growing in logarithmic phase of growth were found to contain a number of phosphorylated proteins . Studies by two-dimensional polyacrylamide gel electrophoresis indicated that the ribosomal proteins phosphorylated in vivo correspond with those phosphorylated in vitro . The relationship of in vivo phsophorylation of ribosomes to the growth and physiology of S . cerevisiae is not known.

Mol Gen Genet, 1976 May 7, 145(2), 169 - 75
Biogenesis of mitochondria . XLII . Genetic analysis of the control of cellular mitochondrial DNA levels in Saccharomyces cerevisiae; Hall RM et al.; The proportion of total cell DNA which is mitochondrial DNA was measured in haploid, diploid and tetraploid strains of S . cerevisiae grown under a standard set of conditions . For all strains tested the mitochondrial DNA level was in the range 16%-25% of total cell DNA . Repeated measurements of the cellular level of mitochondrial DNA in two haploid strains showed that these strains have measurably different cellular mitochondrial DNA levels (17% and 24% of total DNA, respectively) under our conditions . These two grande strains were used to investigate the role of the mitochondrial and nuclear genomes in the regulation of the mitochondrial DNA level . We have shown by genetic analysis that the difference between these two strains is determined by at least two nuclear genes . The mitochondrial genome is not involved in the regulation of cellular mitochondrial DNA levels . A number of purified petite clones derived from independent spontaneous petite isolates of the grande strain which contained 24% mitochondrial DNA were also studied . The mitochondrial DNA levels in all but one of these petites fell in the range 20-25% of total cell DNA . From these results we conclude that, in general, the mitochondrial DNA level in petite strains is controlled by the same mechanism as operates in grande strains . We propose a general model for the control of the cellular mitochondrial DNA level, in which the amount of mitochondrial DNA per cell is determined by regulation of the number of mitochondrial DNA molecules per cell . This regulation is mediated through the availability of a set of nuclear coded components, possibly a mitochondrial membrane site, which are required for the replication of mitochondrial DNA.

Mol Gen Genet, 1976 May 7, 145(2), 159 - 63
Pattern of somatic segregation of the cytoplasmic drug-resistance factors in yeast; Uchida A et al.; The pattern of somatic segregation of the cytoplasmic factors confering resistances to chloramphenicol, erythromycin and oligomyin in S . cerevisiae was studied . The fractions of the zygotes heterozygous for the chloramphenicol-resistance factor and for the erythromycin-resistance factor decreased exponentially with generation number of zygotes . The rate of the segregation was highest for the chloramphenicol-resistance factor and lowest for the oligomycin-resistance factor . The segregation rate as well as the transmission polarity of the chloramphenicol-resistance factor varied with different carbon sources with which the parental haploids were grown prior to mating.

Proc Natl Acad Sci U S A, 1976 May, 73(5), 1664 - 8
Control of cell division in Saccharomyces cerevisiae by methionyl-tRNA; Unger MW et al.; We suggest that two events are necessary for an asynchronous population of cells to undergo arrest in the GI phase of the cell cycle upon nutrient starvation . First, passage through GI must be prevented by a deficiency of some metabolic intermediate . Since this intermediate may act indirectly to arrest division, we designate it the "signal" . We have found three conditions under which Saccharomyces cerevisiae cells arrest division in GI: sulfate starvation of a prototroph, methionine starvation of an auxotroph, or a shift of a conditional methionyl-tRNA synthetase mutant {L-methionine: tRNA Met ligase (AMP-forming), EC 6.1.1.10} to a restrictive condition . We interpret these results to indicate that the signal for sulfate starvation in S . cerevisiae is generated near the end of the sulfate assimilation pathway (at or beyond the formation of mehtionyl-tRNA) . As a unifying hypothesis, we propose that the signal for all nutrients is generated at the level of protein biosynthesis.

Proc Natl Acad Sci U S A, 1976 Feb, 73(2), 386 - 90
Evidence that acyl coenzyme A synthetase activity is required for repression of yeast acetyl coenzyme A carboxylase by exogenous fatty acids; Kamiryo T et al.; The cellular content of acetyl-CoA carboxylase {acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2} in Saccharomyces cerevisiae is reduced by the addition of long-chain fatty acids to the culture medium . Mutant strains of S . cerevisiae defective in acyl-CoA synthetase {acid:CoA ligase (AMP-forming), EC 6.2.1.3} were isolated and used to determine whether fatty acid itself or a metabolite of fatty acid is more directly responsible for the repression of acetyl-CoA carboxylase . Cells of the mutant strains were capable of incorporating fatty acid to an extent comparable to that observed with the wild-type strain, but they accumulated markedly more of the incorporated fatty acid in the nonesterified form than did the wild-type cells . The level of acetyl-CoA carboxylase activity in the mutants, in contrast to that in the wild-type strain, was hardly affected by the addition of fatty acids to the medium . These results indicate that the activation of exogenous fatty acid is required for the repression of acetyl-CoA carboxylase, supporting the view that the repressive effect is mediated by some compound metabolically derived from fatty acid.

Int J Vitam Nutr Res, 1976, 46(2), 115 - 24
{Nutritional study of the membranes of S . cerevisiae . 1 . Chemical composition and viscosity}; Adrian J et al.; After an enzymic auto-degradation of their cytoplasma, the residue of the yeast (S . cerevisiae) contains a thick cell wall and a thin plasma membrane . These total membranes have the following composition in dry substance: proteins = 20,5%, lipids = 31,5%, carbohydrates = 42,0%, and ash = 3,7% . About 85% of carbohydrates (glycans) are easily hydrolysable by chemical method and should be digestible by the non-ruminant species . Proteins, contain 6,9% of lysine, 6,35% of threonine and have only one serious deficit, that of methionine which is 57% . These proteins seem to be resistant to the Maillard reaction . The percentage of in vitro digestible lysine increases when the membranes have undergone a heating of sufficient intensity . The methods of the treatment may give to the membranes an important apparent viscosity . These membranes could play the part of thickening and gelifiant agent in food technology . They also might constitute an interesting source of proteins because of its concentration in lysine and threonine.

Biochimie, 1976, 58(10), 1213 - 20
Effect of genetic and physiological manipulations onthe kinetic and binding parameters of the adenine nucleotide translocator in Saccharomyces cervisiae and Candida utilis; Lauquin G et al.; 1 . Ghe kinetic and binding parameters of adenine-nucleotide transport have been studied in mitochondria isolated from yeast cells in which the mitochondrial protein-synthetizing system had been inhibited by growth in the presence of erythromycin . These parameters have also been studied in promitochondria isolated from yeast grown in anaerobiosis aesence of ethidium bromide results in a loss of cytochromes b, alpha and alpha 3, but it does not affect the rate constant of ADP transport in isolated mitochondria, nor the number of binding sites for atractyloside, bongkrekic acid and ADP . 3 . Promitochondria from S . cerevisiae grown in anaerobiosis, mitochondria from a qo mutant (qo mitochondria) and mitochondria from S . cerevisiae grown in the presence of erythromycin (ERY-mitochondria) are able to transport ADP by the same exchange-diffusion mechanism, sensitive to carboxy-atractyloside, and with the same rate constant as the wild type mitochondria . Promitochondria, qo mitochondria and ERY-mitochondria bind atractyloside, bongkrekic acid and ADP with the same high affinity as the wild type mitochondria . They only differ from the wild type mitochondria by a lower number of binding sites for ADP and for specific inhibitors of ADP transport . 4 . Mitochondria isolated from the nuclear mutant p9 of S . cerevisae, called also op1, are characterized by a much lower affinity for bongkrekic acid than mitochondria from the wild type (20 times less) . 5 . Manipulation of the fatty acid composition of the mitochondrial membranes in the desaturase auxotroph mutant KD115 does not modify the number of sites, no their affinity of bongkrekic acid . 6 . The above results are interpreted to mean that the structure and function of the mitochondrial adN translocator are not affected by any change in the mitochondrial protein synthetizing system.

Biochimie, 1976, 58(1-2), 179 - 82
UGA mutations and UGA suppressors in yeast; Hawthorne DC; Eight UGA alleles have been obtained in S . cerevisiae . Two UGA alleles, ade5,7-143 and gal10-1, were isolated as forward mutations from wildtype . Six UGA alleles, arg4-2' (UGA), his5-2' (UGA), ilv3-1' (UGA), leu2'1' (UGA), lys1-1' (UGA), and asp5-1' (UGA), were derived from UAA alleles by selecting from revertants in the presence of UGA suppressors . With these 8 UGA alleles, two classes of UGA-specific suppressors can be distinguished . Suppressors in one class act upon all 8 allelqs ; while suppressors in the second class act upon all but 3 alleles : ade5,7-143, arg4-2' (UGA), and gal10-1.

Rev Ig Bacteriol Virusol Parazitol Epidemiol Pneumoftiziol Bacteriol Virusol Parazitol Epidemiol, 1976 Jan-Mar, 21(1), 37 - 41
{Study of purified aldolase from Saccharomyces cerevisiae, using irradiated fructose-1,6-diphosphate}; Rabega C et al.; The interaction of an electromagnetic field with the enzymatic substrate-- the sodium salt of fructose-1,6-disphosphate--induces in the latter a new type of physical transition S leads to S . The enzyme, in this case Saccharomyces cerevisiae aldolase, is able to reveal this new state of the substrate by an increase in its specific activity within well established irradiation times . Each enzyme is characterized by the tm (minimal irradiation time of the substrate) a tau (fixed time period) parameters that delimit the two signals . Purified S . cerevisiae aldolase has tm=5 sec . and tau=20 sec., in contrast to muscle aldolase (represented by class I aldolase) which has tm=15 sec . and tau=30 sec . This may be attributed to the fact that most of the enzymatic systems in S . cerevisiae are made up of several distinct molecular forms, involved in more metabolic pathways than in the animal tissue, therefore with various responses to the phenomenon of perturbation of the substrates.

Mol Gen Genet, 1975 Dec 23, 142(1), 1 - 12
Regulation of the ilv 1 multifunctional gene in Saccharomyces cerevisiae; Bollon AP; The ilv 1 gene in S . cerevisiae codes for a regulatory protein involved in depression of the ilv 2 and ilv 3 genes as well as a biosynthetic enzyme, threonine deaminase . 2 . The ilv 1 gene does not autogenously regulate its catalytic product threonine deaninase . 3 . Regulation of the ilv 2 and ilv 3 gene products involve different aporepressors than regulation of the ilv 1 gene product . 4 . The ilv I multifunctional gene in S . cerevisiae may be a duplication and fusion of a bacterial like ilv 1 gene where ilv 1 catalytic and regulatory function have been differentially conserved.

Biochim Biophys Acta, 1975 Dec 17, 409(3), 267 - 73
Substitution of cellular fatty acids in yeast cells by the antibiotic cerulenin and exogenous fatty acids; Awaya J et al.; Cell growth of Saccharomyces cerevisiae ATCC 12341 inhibited by the antibiotic cerulenin, a specific inhibitor of fatty acid and sterol syntheses, was reversed by various exogenous fatty acids . Myristic acid (14 : 0), pentadecanoic acid (15 : 0), palmitic acid (16 : 0), and oleic acid (18 : 1) reversed effectively the growth inhibition by cerulenin . When these cells were reversed by adding pentadecanoic acid, over 90% of native even-numbered fatty acids was substituted by odd-numbered fatty acids . Those in the cells reversed by adding oleic acid were almost all unsaturated fatty acids . Cerulenin did not inhibit either elongation or desaturation systems in S . cerevisiae.

J Bacteriol, 1975 Dec, 124(3), 1545 - 57
Sporulation in D-glucosamine auxotrophs of Saccharomyces cerevisiae: meiosis with defective ascospore wall formation; Whelan WL et al.; Mutants that require exogenous D-glucosamine for growth were isolated from Saccharomyces cerevisiae X2180-1A after ethyl methane sulfonate mutagenesis . Class A auxotrophs fail to grow on yeast extract-peptone-dextrose and minimal media, whereas class B auxotrophs grow on minimal medium and readily revert to grow on yeast extract-peptone-dextrose medium . Class B auxotrophs are suppressible by a class of suppressors distinct from nonsense suppressors, and their properties suggest that they are defective in a regulatory function . All 23 mutants studied were recessive and allelic, and they define a new gene designated gcn1 . An analysis of a class A auxotroph revealed that it lacked L-glutamine:D-fructose 6-phosphate amidotransferase (EC 2.6.1.16) activity and indicates that GCN1 codes the amino acid sequence of this enzyme . The finding that all mutants were allelic indicates that the amidotransferase is the only enzyme responsible for D-glucosamine synthesis in S . cerevisiae . The occurrence of allelic complementation and media-conditional mutants suggests that the amidotransferase is a multimeric enzyme with an activity subject to metabolic control . Diploids homozygous for gcn1 fail to complete sporulation . They proceed through meiosis normally, as judged by the occurrence of meiotic recombination, the production of haploid nuclei, and the formation of multinucleate cells visible after Giemsa staining . However, the formation of glusulase-resistant ascospores is blocked, and deformed spores lacking the electron-dense outer layer characteristic of the normal spore wall are observed by electron microscopy . Cells that acquire the ability to synthesize D-glucosamine, because of gene conversion during meiosis, complete sporulation in a normal fashion . Thus, the GCN1 gene product appears to be synthesized late in sporulation and may prove to be a useful developmental landmark for the termination of ascospore development.

J Bacteriol, 1975 Dec, 124(3), 1411 - 6
Induction of petite mutations during germination and outgrowth of Saccharomyces cerevisiae ascospores; Redshaw RA; The germination and outgrowth of Saccharomyces cerevisiae ascospores were studied by determining the sensitivity of the ascospores to the action of chemical mutagens . Survival of the ascospores after N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment was low during the first 2 h of germination and then increased and remained constant . Survival of the ascospores after 2-methoxy-6-chloro-9-(3-{ethyl-2-chloroethyl}aminopropylamino)acridine-2HC1 (ICR-170) treatment was constant from 0 to 5 h, but as the ascospores completed outgrowth at 6 h they became more sensitive to killing by ICR-170 . Survival of the ascospores remained high during treatment with 2-methoxy-6-chloro-9-(3-{ethyl-2-hydroxyethyl}aminopropylamino)acridine-2HC1 (ICR-170-OH) or 2,7-diamino-10-ethyl-9-phenyl-phenanthridinium bromide . The main classes of mutations screened for were petites and auxotrophs . The induction of petites and auxotrophs by MNNG was independent of the stage of germination and outgrowth treated . Petite induction by ICR-170 was dependent upon the stage of germination and outgrowth treated . The early hours of germination (0 to 3 h) were not sensitive to petite induction . However, there was maximal petite induction at 5 h into germination and outgrowth, followed by a decline . During this same time period, ICR-170 induced less than 1% auxotrophic colonies . This finding is very unusual because ICR-170 induced 15% auxotrophic colonies in starved log-phase cultures of S . cerevisiae . The acridine ICR-170-OH induced no mutations during germination and outgrowth of the ascospores . Ethidium bromide induced petites, and the petite frequency became maximal at 5 h of germination and outgrowth, a result similar to that obtained with ICR-170.

Z Naturforsch {C}, 1975 Nov-Dec, 30(6), 811 - 7
UV-induction of thymine-containing dimers in Saccharomyces cerevisiae; Fath WW et al.; In haploid and diploid S . cerevisiae the dimer yield ratio TT/CT is found to be 1.2/1 and 1.3/1, resp., at the UV (254 nm) unit dose 1 erg/mm2, the share of TT and CT in a UV (254 nm) lethal hit being 0.7 TT and 0.6 CT . A general formulation of the UV lethal hit is given and discussed . The TT+CT yields obtained for S . cerevisiae are compared to those reported for other organisms . It is found that there obviously exists a directly proportional linear correlation between genome size and TT+CT yield for the UV dose range well below the stationary levels of the TT and CT formation kinetics.

Proc Natl Acad Sci U S A, 1975 Oct, 72(10), 3912 - 6
Yeast manno-protein biosynthesis: solubilization and selective assay of four mannosyltransferases; Nakajima T et al.; Using appropriate yeast strains and exogenous acceptors, we have devised specific assays for four mannosyltransferase activities involved in biosynthesis of the carbohydrate outer chain of yeast mannoproteins . The assays utilize GDP-{14C}mannose as the donor and unlabeled oligosaccharides as the acceptors, the products being neutral radioactive oligosaccharides one mannose unit larger than the acceptors . The multiglycosyltransferase system from Saccharomyces cerevisiae was solubilized in Triton X-100 and urea and purified 100-fold . Free mannose is an acceptor for the alpha1 leads to 2-mannosyltransferase, the major product being alpha{14C}Man leads to 2Man . The alpha1 leads to 6-mannooligosaccharides serve as acceptors for both the alpha1 leads to 2- and alpha1 leads to 6-transferases, but the tetrasaccharide alphaMan leads to 3alphsMan leads to 2alphaMan is a specific acceptor for the latter enzyme and yields (see article) . When reduced, this same tetrasaccharide serves as the acceptor for an alpha1 leads to 3-mannosyltransferase from Saccharomyces chevalieri, yielding a pentasaccharide with two terminal 1 leads to 3 linkages . Assay of the alpha1 leads to 3-transferase in S . cerevisiae utilizes reduced alpha1 leads to 2-mannotriose as the acceptor, the product being alpha{14C}Man leads to 3alphaMan leads to 2alphaMan leads to 2Mannitol . The multienzyme system works in concert to make "mannan" in a cell-free in vitro system.

J Bacteriol, 1975 Oct, 124(1), 476 - 83
Membrane-mediated killing of Saccharomyces cerevisiae by glycoproteins from Torulopsis glabrata; Bussey H et al.; Cell-free supernatants from cultures of Torulopsis glabrata contained glycoprotein toxins that killed sensitive and killer strains of Saccharomyces cerevisiae with single-hit kinetics . Growing S . cerevisiae treated with the toxins showed a leakage of cellular potassium, partial dissipation of the adenosine triphosphate pool, and a coordinate shutdown of macromolecular synthesis . These pool efflux-stimulating toxins have been partially purified and at least three toxic glycoproteins have been separated . Pool efflux-stimulating toxin activity was stable from pH 3 through 7, though killing was maximal close to pH 4.

Can J Biochem, 1975 Aug, 53(8), 881 - 9
Nuclear demethylation and C-24 alkylation during ergosterol biosynthesis in Saccharomyces cerevisiae; Fryberg M et al.; The role of 4,4-dimethylzymosterol (3), 4,4-dimethylfecosterol (4) and 31-norlanosterol (5) in the biosynthesis of ergosterol in Saccharomyces cerevisiae has been investigated . The synthesis of 4 and 5 coupled with the availability of 3 facilitated a search for these sterols in commercial yeast sterol concentrates, fresh laboratory grown yeast and fresh brewery grown yeast . Sterol 4 was not detected in any of these mixtures whereas 5 was found in the first and last and 3 was present in all three sources investigated . Investigation of incorporation of {2-3H}lanosterol into 3, 4 and 5 revealed significant incorporation into 3 but neither 4 nor 5 . This observation suggests the principle pathway for ergosterol biosynthesis initially involved 1 leads to 3 leads to 7 . Incubation of a mixture of {2,4-3H}zymosterol and {26,27-14C}lanosterol with S . cerevisiae revealed that during the initial phases of aerobic growth the major route from 7 to ergosterol involves zymosterol (11) but as 11 accumulates 4 alpha-methyl-24-methylenezymosterol (8) assumes equal importance.

Biochim Biophys Acta, 1975 Jul 3, 394(3), 470 - 81
Energy requirements for the uptake of L-leucine by Saccharomyces cerevisiae; Ramos EH et al.; (1) Substrates capable of activating mitochondrial electron transfer and oxidative phosphorylation, namely, pyruvate, acetate, propionaldehyde and butanol, stimulated the concentrative uptake (transport and accumulation) of L-{14-C}leucine by Saccharomyces cerevisiae (wild type strain 207, starved cells) . Under adequate experimental conditions, the L-{14-C}leucine uptake versus the oxygen uptake ratio was almost the same with either pyruvate, acetate or D-glucose as energy sources . Substrate oxidation also increased L-{14-C}leucine incorporation into the cell protein . (2) With S . cerevisiae D261 and D247-2 and propionaldehyde as an energy source, or with strain 207 and glucose as energy source, 2,4-dinitrophenol (50 muM) inhibited L-{14-C}leucine uptake, the inhibition being accompanied by stimulation of respiration . With S . cerevisiae 207 and propionaldehyde as energy source, 2,4-dinitrophenol inhibited both respiration and L-{14-C}leucine uptake, but with respiration being less affected than uptake . Displacement of accumulated L-{14-C}leucine was also inhibited by 2,4-dinitrophenol . (3) In the presence of glucose, and for relatively brief incubation periods, anaerobically grown cells of S . cerevisiae 207 and of a p-minus "petite" mutant of this strain incorporated L-{14-C}leucine with less efficiency than the original wild type strain 207, grown aerobically . With D-glucose as energy source, 2,4-dinitrophenol and iodoacetate inhibited alike L-{14-C}leucine uptake by the respiration competent cells . (4) It is postulated that in respiration-competent yeasts, the mitochondrion contributes to 6-{14-C}leucine uptake by supplying high-energy compounds required for amino acid transport and accumulation . Conversely, the promitochondrion in the anaerobically grown yeast, or the modified mitochondrion in the respiratory deficient mutant, competes for high energy compounds generated by glycolysis in the cytosol.

J Bacteriol, 1975 Jun, 122(3), 1017 - 24
L-Asparaginase of Saccharomyces cerevisiae: an extracellular Enzyme; Dunlop PC et al.; During recent studies conducted with suspensions of three strains of Saccharomyces cerevisiae, it was observed that ammonia was rapidly liberated when L-asparagine was added to the medium . Subsequent investigation has revealed that these strains of S . cerevisiae have an externally active asparaginase as well as an internally active one . The appearance of the external asparaginase is stimulated by nitrogen starvation, requires an available energy source, and is prevented by cycloheximide . The internal enzyme appears to be constitutive . The external activity is relatively insensitive to para-hydroxymercuribenzoate inhibition, whereas the internal activity is highly inhibited by this compound.

Genetics, 1975 Apr, 79(4), 561 - 71
Evidence of preferential pairing of chromosomes at meiosis in aneuploid yeast; James AP et al.; Meiotic pairing in homothallic S . cerevisiae was studied by tetrad analysis, using strains that were trisomic or tetrasomic for chromosomes . I . The disomic segregants of these strains produce tetrasomic spore colonies that can be distinguished by their phenotype . Results indicated the existence of preferential pairing and nonrandom assortment of chromosomes at meisosis I . The frequency of crossing over is apparently normal in at least some regions when nonpreferred pairing occurs.

Genetics, 1975 Apr, 79(4), 661 - 74
Gene duplication as a mechanism of genetic adaptation in Saccharomyces cerevisiae; Hansche PE; It has been shown that specific mutations of the gene that codes for the general acid monophophatase (Aphtase) of S . cerevisiae can increase the affinity of this enzyme for beta-glycerophosphate (BGP) and thereby provide this organism with the capacity to exploit extremely low concentrations of this organic phosphate (Francis and Hansche 1973) . In this report two additional avenues are demonstrated to be available to this organism for increasing its capacity to exploit low concentrations of organic phosphates . One avenue is through mutations that increase the amount of Aphtase that associates with the cell wall, where it catalizes the hydrolysis of exogenous organic phosphates . The other avenue is through duplication of the gene that codes for Aphtase, doubling the amount of Aphtase synthesized.--The spontaneous duplication of the structural gene of Aphtase and the incorporation of the duplicate into this experimental population as a means of exploiting low concentrations of exogenous organic phosphates provides direct support for the first step of the mechanism through which new metabolic functions are postulated to evolve.

J Bacteriol, 1975 Feb, 121(2), 562 - 70
Positive selection of general amino acid permease mutants in Saccharomyces cerevisiae; Rytka J; It was found that D-stereoisomers of natural amino acids inhibit the growth of Saccharomyces cerevisiae cells . Kinetic and genetic evidence showed that d-amino acids enter the cell by the general amino acid permease . Two classes of S . cerevisiae mutants resistant to d-amino acids were isolated . One class of mutants appeared to be defective in the general amino acid permease specified by the gene gap . In the second class, the activity of general amino acid permease was affected by ammonium ions . Mutants of the second class were isolated in a yeast strain with the general amino acid permease insensitive to the presence of ammonium ions in culture media . The mutation affecting the permease, amc, occurred in a locus unlinked to gap.

Antonie Van Leeuwenhoek, 1975, 41(2), 147 - 51
The occurrence of killer character in yeasts of various genera; Philliskirk G et al.; Species of 7 of the 28 yeast genera in the National Collection of Yeast Cultures exhibited killing activity against Saccharomyces cerevisiae . The highest incidence of killer yeasts was found in the genus Hansenula (12 of the 29 strains examined) . Saccharomyces, the best represented genus in the Collection, showed a low incidence of killer activity and many of the killer strains are hybrids with a common S . cerevisiae parent . The activities of culture filtrates of the 59 killer yeast isolated responded differently to pH and four types of response were recognised.

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