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PubMed2002

Spectrum and proteinase production of yeasts causing vaginitis in Saudi Arabian women.

BACKGROUND: Yeast vaginitis is a common infection. Data on the identity and prevalence of the etiological species would serve both epidemiological and therapeutic ends. Proteinase secretion by the invading yeast has been implicated in facilitating infection. Hence a prospective study was conducted to determine the species causing vaginitis in women from Saudi Arabia and the yeast's ability to produce proteinase. MATERIAL/METHODS: The subjects were patients with clinical signs of vaginitis. A high vaginal swab specimen from each patient was cultured, and only women yielding heavy yeast growth were enrolled. The isolated yeasts were identified by routine procedures, then evaluated for proteinase production in a medium containing bovine serum albumin. RESULTS: A total of 500 patients were studied. Candida albicans was the major species to cause vaginitis (59%), followed by C. glabrata (31%), C. tropicalis (4%), C. krusei (3.2%), Saccharomyces cerevisiae (1.6%), C. parapsilosis (0.6%), and C. kefyr (0.6%). All isolates of C. albicans and C. parapsilosis and 95% of C. tropicalis produced proteinase, while isolates from the remaining species did not. CONCLUSIONS: These results indicate that 59.6% of yeast vaginitis in women from Saudi Arabia is caused by C. albicans, and 31.6% by C. glabrata. Of relatively low prevalence were C. tropicalis and C. krusei. The study also revealed that both proteinase producers and non-producers were involved in causing vaginitis, indicating that proteinase secretion is not an essential factor in the pathogenesis of yeast vaginitis.

Adolescent↗
PubMed2002

Inhibition of human phosphodiesterase 4A expressed in yeast cell GL62 by theophylline, rolipram, and acetamide-45.

AIM: To study the inductive expression of human phosphodiesterase 4A (hPDE4A) in yeast cell GL62 and investigate the inhibitory effects of theophylline, rolipram, and acetamide-45 on PDE4A activity of the expressed product in yeast cell GL62. METHODS: Yeast cell GL62 were transfected with human PDE4A gene cloned in the expression plasmid p138NB. Expression was induced by adding CuSO4 to a final concentration of 150 micromol/L, and the expressed product was extracted. The activity of PDE4A was detected by HPLC. RESULTS: Yeast cell GL62 expressed a certain protein at CuSO4 150 micromol/L, the size of the expressed product was between 62 kDa and 83 kDa, the activity of PDE4A of the expressed product at 3 h was in maximum (188 23) micromol/g/min, and the Km was (17.7 2.6) micromol/L. Theophylline, rolipram, and acetamide-45 could inhibit the activity of PDE4A extracted from yeast cell GL62. The IC50 (95 % confidence limits) of theophylline, rolipram, and acetamide-45 were 1642 (989-2727), 4.58 (3.45-6.08), and 275 (170-444) micromol/L respectively. CONCLUSION: PDE4A expressed in yeast cell GL62 is biologically active. Theophylline, rolipram, and acetamide-45 can inhibit the PDE4A activity. The expressed product in yeast cell GL62 may be used in the research work of PDE4 and its inhibitors.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2002

Correlation of the density of yeast Malassezia with the clinical severity of seborrhoeic dermatitis.

OBJECTIVE: To correlate the density of the yeast Malassezia with the clinical seventy of seborrhoeic dermatitis. METHOD: Fifty patients and twenty control subjects were selected for the study. The patients were evaluated both clinically for the severity of seborrhoeic dermatitis and microscopically for the presence of the yeast Malassezia. RESULTS: Out of 50 patients Malassezia was present in 41 patients (82%). On microscopic evaluation it was found that patients with mild seborrhoeic dermatiis had a density of 2+ (more than 5 but less than 10 yeast cells per high power field (hpf). Patients with moderate seborrhoeic dermatitis had a density of 3+ (more than 10 but less than 20 yeast cells per hpf) and patients with severe seborrhoeic dermatitis had a density of 4+ (more than 20 yeast cells per hpf). Of the 20 normal subjects only 8 (40%) had Malassezia and they had a density of 1+ (5 or fewer yeast cells per hpf). The results show a strong correlation of the yeast Malassezia to the severity of seborrhoeic dermatitis (p value < 0.05). CONCLUSION: Malassezia increases in proportion with the severity of seborrhoeic dermatitis; an antifungal agent should therefore be used in the treatment of seborrhoeic dermatitis.

Adolescent↗
PubMed1992

Organella-targeted expression of rat liver cytochrome P450c27 in yeast. Genetically engineered alteration of mitochondrial P450 into a microsomal form creates a novel functional electron transport chain.

A modified rat cytochrome P450c27, whose mitochondrial targeting signal had been replaced by a possible microsomal targeting signal of bovine cytochrome P450c17, was expressed in yeast. The modified P450c27 hemoprotein was correctly localized on yeast microsomes and exhibited the P450c27-dependent monooxygenase activity by addition of bovine adrenodoxin (ADX) and NADPH-adrenodoxin reductase (ADR). Considering the previous observation that P450c27 with its own mitochondrial targeting signal was imported into yeast mitochondria (Akiyoshi-Shibata, M., Usui, E., Sakaki, T., Yabusaki, Y., Noshiro, M., Okuda, K., and Ohkawa, H. (1991) FEBS Lett. 280, 367-370), it is now suggested that the destination of P450c27 to either mitochondria or microsomes in yeast depends solely on the amino-terminal targeting signal. In addition, the modified P450c27 was simultaneously expressed in yeast with mature forms of bovine ADX and ADR. The recombinant yeast produced the P450 on the microsomes and mature forms of ADX and ADR in the cytoplasm, and showed the monooxygenase activity. Accordingly, a novel type of functional electron transport chain has been established between the cytoplasm and the microsomes in yeast.

Animals↗
PubMed1992

Identification of the yeast TOP3 gene product as a single strand-specific DNA topoisomerase.

The TOP3 gene of the yeast Saccharomyces cerevisiae was postulated to encode a DNA topoisomerase, based on its sequence homology to Escherichia coli DNA topoisomerase I and the suppression of the poor growth phenotype of top3 mutants by the expression of the E. coli enzyme (Wallis, J.W., Chrebet, G., Brodsky, G., Golfe, M., and Rothstein, R. (1989) Cell 58, 409-419). We have purified the yeast TOP3 gene product to near homogeneity as a 74-kDA protein from yeast cells lacking DNA topoisomerase I and overexpressing a plasmid-borne TOP3 gene linked to a phosphate-regulated yeast PHO5 gene promoter. The purified protein possesses a distinct DNA topoisomerase activity: similar to E. coli DNA topoisomerases I and III, it partially relaxes negatively but not positively supercoiled DNA. Several experiments, including the use of a negatively supercoiled heteroduplex DNA containing a 29-nucleotide single-stranded loop, indicate that the activity has a strong preference for single-stranded DNA. A protein-DNA covalent complex in which the 74-kDa protein is linked to a 5' DNA phosphoryl group has been identified, and the nucleotide sequences of 30 sites of DNA-protein covalent complex formation have been determined. These sequences differ from those recognized by E. coli DNA topoisomerase I but resemble those recognized by E. coli DNA topoisomerase III. Based on these results, the yeast TOP3 gene product can formally be termed S. cerevisiae DNA topoisomerase III. Analysis of supercoiling of intracellular yeast plasmids in various DNA topoisomerase mutants indicates that yeast DNA topoisomerase III has at most a weak activity in relaxing negatively supercoiled double-stranded DNA in vivo, in accordance with the characteristics of the purified enzyme.

Base Sequence↗
PubMed2004

[Screening hepatitis B virus X-interactive proteins by yeast two-hybrid system].

BACKGROUND & OBJECTIVE: Hepatitis B virus-encoded X protein is a promiscuous transactivator and contributes to the development of hepatocellular carcinoma. Protein-protein interaction seems to be crucial for HBx transactivation. The aim of this study was to screen and identify the proteins which interact with hepatitis B virus (HBV) X protein by yeast two-hybrid system. METHODS: HBV X gene was amplified by polymerase chain reaction (PCR). HBV X bait plasmid, named pAS2-1-X, was constructed by yeast-two hybridization system 3 and verified by sequencing. pAS2-1-X was transformed into the yeast AH109, and X-BD fusion protein expressed in the yeast cells was confirmed by Western blot analysis. Yeast cells cotransformed with pAS2-1-X and normal human liver cDNA library were cultured in selective SC/-trp-leu-his-ade medium. The second screening was performed with beta-gal activity detection. The false positive clones were eliminated by segregation analysis and mating experiment. The real positive clones were amplified, sequenced, and analyzed with bioinformatics. RESULTS: Bait plasmid pAS2-1-X was successfully constructed. The result of Western blot analysis confirmed that pAS2-1-X correctly expressed X-BD fusion protein in the transformed yeast AH109. Ninety-seven clones grew in the selective SC/-trp-leu-his-ade medium; however, only one clone past through the beta-gal activity detection, segregation analysis, and mating experiment. The inserted cDNA fragment of positive clone showed high homology with Fis gene. CONCLUSION: Fis protein is a novel protein which can interact with X protein in vivo by yeast two-hybrid system.

Gene Library↗
PubMedDate not supplied

Induction of apoptosis in breast cancer cells by Saccharomyces cerevisiae, the baker's yeast, in vitro.

The present study was undertaken to evaluate the effect of phagocytosis of killed yeast on the induction of apoptosis in human metastatic breast cancer cells (MCF-7 and ZR-75-1) and non-metastatic breast cancer cells (HCC70). Heat-killed Saccharomyces cerevisiae, baker's and brewer's yeast, was cultured with cancer cells at a ratio of yeast to cancer cells = 10:1, and the percent apoptotic cancer cells was determined by flow cytometry and cytospin preparation. Upon phagocytosis of yeast, breast cancer cells underwent apoptosis. Induction of apoptosis was time- and dose-dependent. Apoptosis was detected as early as 0.5 h (13%), increased to 19% at 2 h and peaked (38%) at 4 h. Metastatic cancer cells were found to be more susceptible to yeast-induced apoptosis than non-metastatic cells; 629% increase for MCF-7 as compared to cells alone, 258% for ZR-75 cells, while HCC70 cells showed a 178% increase. Phagocytosis is associated with the disruption of mitochondrial membrane potential and activation of initiator and effector caspases 8, 9 and 3. However, inhibitors of these caspases did not inhibit yeast-induced apoptosis in cancer cells, suggesting that yeast induces apoptosis in breast cancer cells by a mechanism that is independent of caspase activation. This data may have clinical implications.

Apoptosis↗
PubMed2004

[Vitamin B1 and B2 ratio as a method of brewer's and food yeast identification].

The data on vitamins B1 and B2 content in dry brewer's and baker's yeast are submitted. Their significance as these nutrients source is evaluated. Brewer's yeast are mainly the source of vitamin B1 while baker's yeast--the source of vitamin B2. 5 g of yeast give 10 per cent of vitamin B1 and B2 daily recommended allowance correspondingly. Vitamin B1 and B2 ratio has been proposed as a identification criteria of brewer's and baker's yeast. Ratio more than 1.0 gives evidence that this is brewer's yeast. Vitamin B1 content 4 mg per 100 g or more and at the same time vitamin B1 and B2 ratio exceeding 3.0 demonstrate high quality of brewer's yeast.

Food Microbiology↗
PubMed2005

[Continuous ethanol fermentation using self-flocculating yeast strain and bioreactor system composed of multi-stage tanks in series].

A continuous ethanol fermentation system composed of four-stage tank fermentors in series and with a total working volume of 4000 mL was established. The first fermentor was designated as the seed fermentor and the others for ethanol fermentation. A self-flocculating yeast strain developed by protoplast fusion of Saccharomyces cerevisiae and Schizosaccharomyces pombe was applied. Two-stage corn powder enzymatic hydrolyzate containing reducing sugar 100 g/L, together with 2.0 g/L (NH4)2HPO4 and KH2PO4, was used as yeast seed culture medium and fed into the seed fermentor at the dilution rate of 0.017h (-1). Meanwhile, the hydrolyzate containing reducing sugar 220 g/L, added with 1.5 g/L (NH4)2HPO4 and 2.5 g/L KH2PO4, was used as ethanol fermentation substrate and fed into the second fermentor at the dilution rates of 0.017, 0.025, 0.033, 0.040 and 0.050 h(-1) (based on the total working volume of the three fermentors), respectively. The chemostat states on which all of the monitoring parameters, including residual sugar, ethanol and yeast cell biomass concentrations, were maintained relatively constant were observed for seed cultivation and ethanol fermentations when the fermentation system was operated at the dilution rates of 0.017, 0.025, 0.033 and 0.050 h(-1). Yeast cells were observed being partly immobilized because significant yeast cell biomass concentration differences between the broth out of and inside the fermentors were detected. Moreover, the oscillations of residual sugar, ethanol and yeast cell biomass concentrations were observed when the fermentation system was operated at the dilution rate of 0.040 h(-1). The broth containing more than 12% (V/V) ethanol and less than 0.11% (W/V) residual reducing sugar and 0.35% (W/V) residual total sugar was produced when the dilution rate was controlled at no more than 0.033 h(-1). The ethanol productivity was calculated to be 3.32(g x L(-1) x h(-1)) for the dilution rate of 0.033 h(-1), which increased nearly 100% compared with that for conventional ethanol fermentation technologies using freely suspended yeast cells.

Bioreactors↗
PubMed2005

[Effect of flocculence of a self-flocculating yeast on its tolerance to ethanol and the mechanism].

Investigation was undertaken for the purpose of examining any possible correlation between flocculence of a self-flocculating fusant of Schizosaccharomyces pombe mutant and Saccharomyces cerevisiae mutant (called fusant SPSC for short) and the tolerance of this strain to ethanol. When exposed to 18% (V/V) ethanol for 7 h at 30 degrees C, 52%, 37% and 9% of viability levels remained for the cells of fusant SPSC and its two parental strains, Sch. pombe mutant and S. cerevisiae mutant respectively. Analysis of phospholipid fatty acid composition of plasma membrane showed that the content of palmitic acid of each flocculating yeast (fusant SPSC or Sch. pombe mutant) was around 2-fold higher than that of free S. cerevisiae mutant, with remarkably lower contents of palmitoleic and oleic acids than the latter. When 0.1 mol/L sodium citrate was initially included in the medium in which cells of each flocculating yeast were grown, free cells rather than aggregates were finally obtained. Furthermore, the content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast was found to decrease significantly, with a marked increase in the contents of palmitoleic and oleic acids. As a result, the characteristics of the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast were similar to those of S. cerevisiae mutant. Meanwhile, the disappearance of flocculence of each flocculating yeast caused by the action of sodium citrate brought about a steeply decreased tolerance of the free cells to ethanol, thus being equivalent to that of S. cerevisiae mutant. These data suggest that the stronger ethanol tolerance of each flocculating yeast is related to the higher content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes. Thus, the enhancement by flocculence on the tolerance of yeast cells to ethanol as well as its mechanism are first reported in this work.

Bioreactors↗
PubMed1991

Nucleosome fractionation by mercury affinity chromatography. Contrasting distribution of transcriptionally active DNA sequences and acetylated histones in nucleosome fractions of wild-type yeast cells and cells expressing a histone H3 gene altered to encode a cysteine 110 residue.

A technique for the separation of transcriptionally active and inactive nucleosomes by mercury affinity chromatography has been applied to study the nucleosomal distribution of DNA sequences from the GAL1, ACT1, HIS4, MAT alpha, and HMRa genes of yeast. In mammalian cells, the method has been shown to separate active from inactive nucleosomes and to fractionate the active nucleosomes into two classes, one retained on the mercury column because of salt-labile associations with certain thiol-reactive non-histone proteins, and the other bound by covalent linkage of the cysteine 110 thiol groups of histone H3 molecules to the mercurated support. The first class of nucleosomes is elutable in 0.5 M NaCl; the second is displaced by 10 mM dithiothreitol (DTT) (Walker, J., Chen, T. A., Sterner, R., Berger, M., Winston, F., and Allfrey, V.G. (1990) J. Biol. Chem. 265, 5736-5746). We show that, in wild-type yeast cells, in which histone H3 lacks cysteinyl residues, very little DNA and a negligible complement of nucleosomes appear in the DTT-eluate, confirming the requirement for the H3-thiols in the mercury-binding reaction. Moreover, the DTT-eluted fraction is seriously deficient in the actively transcribed GAL1, ACT1, HIS4, and MAT alpha DNA sequences. Site-directed mutagenesis was employed to create an H3 gene containing a cysteine codon in place of the alanine codon at position 110 of the yeast H3 amino acid sequence. A strain was constructed containing the mutant histone H3 gene instead of the normal H3 gene. Subsequent fractionations of the mutant nucleosomes by mercury-affinity chromatography revealed a characteristic nucleosome peak in the DTT-eluted fraction. Its content of transcribed GAL1, ACT1, and HIS4 DNA sequences was 20- to 500-fold higher than that of the corresponding DTT-eluted fraction of wild-type yeast. Although this result is in accord with the finding that, in mammalian cells, the thiol groups of histone H3 become accessible when nucleosomes "unfold" during transcription, we find that nucleosomes containing the GAL1 DNA sequences of the yeast H3-mutant also bind to the mercury column when that gene is not being expressed. We conclude that many yeast nucleosomes are maintained in a "primed," potentially active state, possibly due to the very high constitutive levels of acetylation of the core histones. However, the nucleosomes of the HMRa gene, which is not expressed in a MAT alpha yeast strain, are virtually absent from the DTT-eluted nucleosome fractions of the H3-mutant cells, indicating that prolonged silencing of the gene is accompanied by compaction and loss of H3-thiol reactivity of its nucleosomes.

Acetylation↗
PubMed1990

Characterization of a nonglycosylated single chain urinary plasminogen activator secreted from yeast.

Using site-directed mutagenesis, we have changed the asparagine in human single-chain urinary plasminogen activator (u-PA) at position 302 to an alanine. This alteration removes the only known amino acid residue glycosylated in the protein. The single-chain u-PA containing an alanine residue at position 302 instead of asparagine (scu-PA(N302A] cDNA gene was expressed in the yeast Saccharomyces cerevisiae. Secretion of the protein product into the culture broth was achieved by replacing the human secretion signal codons with those from yeast invertase, adding a yeast promoter from the constitutively expressed glycolytic genes triosephosphate isomerase or phosphoglycerate kinase, and integrating multiple copies of these transcriptional units into the genome of yeast strains carrying the "supersecreting" mutation ssc1. When fermented in a fed-batch mode, these recombinant baker's yeast strains secreted scu-PA(N302A) in a strongly growth-associated manner. Greater than 90% of the u-PA found in the culture broth was in the single-chain form. Scu-PA(N302A) was purified to homogeneity using two chromatography steps. The purified protein had a molecular weight of 47,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and lacked any detectable N-linked glycosylation. The in vitro fibrinolytic properties of scu-PA(N302A) were found to be essentially equivalent to those of natural single-chain u-PA derived from the human kidney cell line TCL-598. Since scu-PA(N302A) lacks the immunogenic N-linked carbohydrate pattern of yeast, it may be a useful therapeutic agent which can be produced economically by yeast fermentation.

Amino Acid Sequence↗
PubMed1975

The polyadenylate polymerases from yeast.

Poly(A) polymerase activity was first detected in yeast extracts, primarily in association with the ribosomal fraction, by Twu and Bretthauer in 1971 (Twu, J. S., and Bretthauer, RK. (1971) Biochemistry 10, 1576-1582). This activity has now been separated into three distinct enzymes by chromatography on DEAE-cellulose. Each of the three enzymes can catalyze the incorporation of adenylate residues from ATP into a polyadenylate (poly(A)) tract at the 3' terminus of a primer RNA. Enzyme I elutes at 0.07 M ammonium sulfate from the DEAE-cellulose column, utilizes the mixed polynucleotide poly(A,G,C,U) or ribosomal RNA most efficiently in vitro, and may be responsible in vivo for the initiation of the poly(A) tracts found on yeast messenger RNA. Enzyme II elutes from the column at 0.20 M ammonium sulfate, requires poly(A) itself or an RNA primer containing a 3'-oligo(A) tract, and may be responsible in the nucleus for the elongation of tracts initiated by enzyme I. Enzyme III elutes from the column at 0.56 M ammonium sulfate and is present in low amounts in nuclear extracts. It may be involved in adding poly(A) tracts to messenger RNA in mitochondria. These enzymes also have the intrinsic capacity for the incorporation of cytidylate residues from CTP, which correlates with the finding of cytidylate residues in the poly(A) tracts present in the yeast RNA which is rapidly labeled in vivo. About 75% of the total poly(A) polymerase activity of yeast is enzyme I, most of which is present in the soluble protein fraction of the whole yeast extract. About 20% of the total poly(A) polymerase is enzyme II, and 1 to 5% is enzyme III. All three of the yeast poly(A) polymerases require an RNA primer with a free 3'-hydroxyl group, show no requirement for a DNA template, require Mn-2+ for optimal activity, have pH optima of 8.5, and are inhibited by GTP, CTP, UTP, and native yeast DNA. Polymerases I and II have similar molecular weights by gel filtration.

Adenosine Triphosphate↗
PubMed1989

Sensitivity of yeasts to amphotericin B and 5-fluorocytosine.

One hundred and forty-four clinical yeast isolates were tested for antifungal susceptibility to Amphotericin B (AMB) and 5-Fluorocytosine (5FC). 61% (88 of 144) of the total yeast isolates were C. albicans. Yeasts were most frequently isolated from high vaginal swabs. High vaginal swabs constituted 64% (92 of 144) of the total number of specimens. Antifungal susceptibility testing of yeasts was conducted by employing an agar dilution technique. 76% (67 of 88) of C. albicans demonstrated MIC values of less than or equal to 1.0 ug/ml to 5FC. All yeasts tested against AMB demonstrated MICs of less than or equal to 0.25 ug/ml. Resistance to 5FC and AMB was defined as any isolate demonstrating an MIC of greater than 16 ug/ml and MIC greater than or equal to 2 ug/ml respectively. Based on this definition approximately 6% of total yeasts and 8% of C. albicans were resistant to 5FC. All yeasts tested were sensitive to AMB.

Amphotericin B↗
PubMed1985

Characterization of an RNA polymerase I-dependent promoter within the spacer region of yeast ribosomal cistrons.

Nucleotide sequences which are required for RNA polymerase I-dependent selective initiation of transcription in vitro from a site within the spacer region of cloned yeast ribosomal DNA have been identified. Yeast rDNA templates containing deletion mutations extending from restriction endonuclease cleavage sites located upstream and downstream from the transcriptional initiation site were constructed. The ability of these mutant templates to support selective transcription in vitro was determined using a yeast whole cell extract. Nucleotide sequences which are required for selective transcription in vitro are within a 22-base pair region which is located immediately adjacent to the transcriptional initiation site. The 3' boundary of this 22-base pair sequence was mapped within a single base pair and resides within the transcribed portion of the rDNA. Nucleotide sequences upstream and downstream from the 22-base pair region are not required for selective transcription and do not appear to affect the efficiency of transcription in vitro. A hybrid plasmid containing only 32 base pairs of yeast rDNA, which includes the 22-base pair region, supports efficient and accurate RNA polymerase I-dependent transcription in vitro. These data demonstrate that the 22-base pair region of yeast rDNA is sufficient for accurate initiation of transcription in vitro. The transcriptional properties of several cloned rDNA templates isolated from two haploid yeast strains and a strain of bakers' yeast were examined. Four cistrons were identified which differ in nucleotide sequence. Three cistrons contain the 22-base pair promoter region and they support selective transcription in vitro. The fourth cistron does not support selective transcription in vitro and contains a single base pair substitution within the 22-base pair promoter sequence.

Base Sequence↗
PubMed1977

DNA polymerases from bakers' yeast.

Two DNA polymerases are present in extracts of commercial bakers' yeast and wild type Saccharomyces cerevisiae grown aerobically to late log phase. Yeast DNA polymerase I and yeast DNA polymerase II can be separated by DEAE-cellulose, hydroxylapatite, and denatured DNA-cellulose chromatography from the postmitochondrial supernatants of yeast lysates. The yeast polymerases are both of high molecular weight (greater than 100,000) but are clearly separate species by the lack of immunological cross-reactivity. Analysis of associated enzyme activities and other reaction properties of yeast DNA polymerases provides additional evidence for distinguishing the two species. Enzyme I has no associated nuclease activity but does carry out pyrophosphate exchange and pyrophosphorolysis reactions, and has an associated 3'-exonuclease activity. Enzyme I does not degrade deoxynucleoside triphosphates and cannot utilize a mismatched template. Enzyme II does carry out a template-dependent deoxynucleoside triphosphate degradation reaction and can excise mismatched 3'-nucleotides from suitable template systems. Earlier studies have shown that both Enzyme I and Enzyme II are inhibited by N-ethylmaleimide. The yeast enzymes are not identical to any known eukaryotic or prokaryotic DNA polymerases. In general, Enzyme I appears to be most similar to eukaryotic DNA polymerase alpha and Ezyme II exhibits properties of prokaryotic DNA polymerases II and III.

DNA Polymerase I↗
PubMed1987

Gene for yeast glutamine tRNA synthetase encodes a large amino-terminal extension and provides a strong confirmation of the signature sequence for a group of the aminoacyl-tRNA synthetases.

The gene for the yeast Saccharomyces cerevisiae glutamine tRNA synthetase is shown here to encode a protein of 809 amino acids. This contrasts with the 551 amino acids of the Escherichia coli glutamine tRNA synthetase. The yeast GLN4 transcripts have 5' termini that start approximately 25 nucleotides in front of the long open reading frame. Much of the extra size of the yeast enzyme is due to a large amino-terminal extension. At codon 225, the yeast enzyme aligns with the amino terminus of the E. coli protein. From this point on, the two sequences have an average of 40% identity, with a few small gaps for alignment, until their respective carboxyl termini. At codon 254 of the yeast and codon 30 of the E. coli enzyme, however, there starts an exact 15-amino acid match between the two proteins. This match encompasses and is partially the same as a short sequence which is a signature sequence for the amino acid group of the bacterial aminoacyl-tRNA synthetases which are specific for different amino acids. This is the strongest sequence match found between any yeast cytoplasmic or mitochondrial aminoacyl-tRNA synthetase with its bacterial homologue. This region of the structure is associated with a nucleotide fold. The result provides strong validation of the signature sequence, especially for sequences where the homology relationships are less dramatic than in this example. Because the 224-amino acid extension of the yeast enzyme does not align with any part of the E. coli enzyme, we propose that it is not associated directly with the catalytic function of the enzyme. Its possible function is investigated in the accompanying paper.

Amino Acid Sequence↗
PubMed1977

[Role of propionic acid, yeasts and ethyl alcohol in regulating the activity of H-factor in Drosophila simulans].

Effects of yeast, propionic acid and ethanol on the activity of H-factor, which sharply increases the frequency of somatic recombination in X-chromosomes of dorsal prothoracal disc cells in Drosophila simulans are studied. The frequency of yellow and singed mosaic spots in heterozygous yw ++/++sn1vHD. melanogaster females, inherited H-factor from the father (the stock sn1v) is estimated. The results of the varience analysis have shown that yeast and propionic acid regulate the activity of H-factor in cells of dorsal prothoracal disc, the interaction of yeast and propionic acid being also observed. Yeasts (or some unknown product of their metabolism) are the activator of H-factor; thus, when larvae eat much yeast, the frequency of yellow and singed mosaic spots in humeral region becomes high. A decrease of mosaic spot frequency under the increase of propionic acid content in nutrition medium is a result of the inhibitory effect of propionic acid on the yeast growth, but not of the direct repression of H-factor activity. So, propionic acid may be considered as a regulator of the second order. Ethanol does not activate H-factor. Changes in the content of yeast and propionic acid in nutrition medium do not affect the frequency of yellow and singed mosaic spots in other regions of D. simulans body, except humeral.

Animals↗