摘要:

AbstractThe relationship between the pathways of glucose and galactose utilization inSaccharomyces cerevisiaehas been studied. Galactose (which is transported and phosphorylated by inducible systems) is a strong inhibitor of the utilization of glucose, fructose and mannose (which have the same constitutive transport and phosphorylation systems). Conversely, all these three hexoses inhibit the utilization of galactose, though with poor efficiency. These cross‐inhibitions only occur in yeast adapted to galactose or in galactose‐constitutive mutants.The efficiency of galactose as inhibitor is even greater than the efficiencies of each of the other three hexoses to inhibit the utilization of each other. Phosphorylation is not involved in the inhibition and the transport of sugars is the affected step.The cross‐inhibitions between galactose and either glucose, fructose or mannose do not implicate utilization of one hexose at the expense of the other, as it occurs in the mutual interactions between the latter three sugars. It seems that, by growing the yeast in galactose, a protein component is synthesized, or alternatively modified, that once bound to either galactose or any one of the other three hexoses (glucose, fructose or mannose), cross‐interacts respectively with the constitutive or the inducible transport systems, impairing their f

ISSN:0749-503X    

DOI:10.1002/yea.320090202

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractVacuoles were isolated fromYarrowia lipolyticayeast cells taken at various growth phases under carbon or nitrogen limitation. Vacuoles from the cells at the logarithmic growth phase showed a high activity of vacuolar H+‐ATPase (0·9–1·1 U/mg protein) and efficiently generated chemical proton gradient and membrane potential across the tonoplast. Ca2+‐ and citrate transport were found to be maximal at this growth phase. At growth retardation and then in the stationary phase all the parameters studied decreased irrespective of the method of growth limitation. The citrate‐transporting activity of vacuoles completely disappeared at growth retardation, also irrespective of the limitation method and irrespective of whether yeast cells overproduced citrate in the culture medium. The citrate‐transporting system ofY. lipolyticavacuolar membrane is concluded not to be involved in citrate efflux and this efflux is probably performed by the plasmalemma trans

ISSN:0749-503X    

DOI:10.1002/yea.320090203

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSaccharomyces cerevisiaecell envelope polyphosphatase was isolated in highly active and stable form by extraction from cells with zwittergent TM‐314 followed by chromatography of the extract on phosphocellulose and QAE‐Sephadex in the presence of 5 mM‐MgCl2, 0·5 mM‐EDTA and 0·1% Triton X‐100. The enzyme possessed a specific activity of 220 U/mg and after 30 days retained 87% of its activity at −20°C. Polyphosphatase molecular mass was determined to be about 40 kDa by gel filtration and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme hydrolysed polyphosphates with various chain lengths (n= 3–208), had low activity for GTP and did not split pyrophosphate, ATP andp‐nitrophenylphosphate. On polyphosphates with chain lengthsn= 3, 9 and 208,Kmvalues were 1·7 × 10−4, 1·5 × 10−5and 8·8 × 10−7M respectively. Polyphosphatase was most active and stable at pH 6·0–8·0. The enzyme showed maximal activity at 50°C. The time of half inactivation of polyphosphatase at 40, 45 and 50°C was 45, 10 and 3 min, respectively. In the absence of divalent cations and also with Ca2+or Cu2+, the enzyme showed practically no activity. The ability of divalent cations to activate polyphosphatase was reduced in the following order: Co2+>Mg2+>Mn2+>Fe2+>Zn2+. Polyphosphatase was completely inhibited by 1 mM‐ammonium molybdate and 50

ISSN:0749-503X    

DOI:10.1002/yea.320090204

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have isolated a single gene from the yeastSaccharomyces cerevisiaeencoding a potential 800 amino acid polypeptide of calculated Mr90 098 Da. This protein consists of an N‐terminal region that shares significant homology with the catalytic domains of several serine‐ and threonine‐specific protein kinases, as well as a large, unique, C‐terminal domain of unknown function. Haploid disruption mutants are viable and do not exhibit any readily observable growth defects under varying conditions of temperature, nutrients or osmotic strength. Due to the apparent structural similarity between this kinase and the protein products of theKIN1andKIN2genes, we have chosen to name this new g

ISSN:0749-503X    

DOI:10.1002/yea.320090205

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have isolated a gene (CAM1) from the yeastSaccharomyces cerevisiaethat encodes a protein homologous to the translational cofactor elongation factor‐1γ (EF‐1γ) first identified in the brine shrimpArtemia salina. The predicted Cam1 amino acid sequence consists of 415 residues that share 32% identity with theArtemiaprotein, increasing to 72% when conservative substitutions are included. The calculated Mrof Cam1p (47 092 Da) is in close agreement with that of EF‐1γ (Mr= 49 200 Da), and hydropathy plots of each protein exhibit strikingly similar profiles. Disruption of theCAM1locus yields four viable meiotic progeny, indicating that under normal growth conditions the Cam1 protein is non‐essential. Attempts to elicit a translational phenotype have been unsuccessful. Since EF‐1γ participates in the regulation of a GTP‐binding protein (EF‐1α), double mutants withcam1disruptions and various mutant alleles of known GTP‐binding proteins were constructed and examined. No evidence was found for an interaction ofCAM1withTEF1, TEF2, SEC4, YPT1, RAS1, RAS2, CDC6, ARF1, ARF2orCIN4. The possibility that Cam1p may play a redundant role in the regulation of protein synthesis or another GTP‐dependen

ISSN:0749-503X    

DOI:10.1002/yea.320090206

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractCatabolite repression and derepression on δ‐aminolevulinate synthase (ALA‐S) and δ‐aminolevulinate dehydratase (ALA‐D) in a normal yeast strain, D27, and its derived D27/C6 (HEM R+) were investigated. ALA‐S and ALA‐D activities and intracellular ALA (I‐ALA) at different physiological states of the cells were measured. In YPD medium, under conditions of repression and when glucose was exhausted, both strains behaved identically as if the mutation was not expressed. In YPEt medium, however, both ALA‐S and ALA‐D activities were higher than in YPD, but the I‐ALA content and the enzymic activity profiles shown by the two strains were quite different. It appears, therefore, that the mutation causes a deregulation of ALA‐S, so that its activity is kept at a high level throughout the cell cycle. This would explain the increased levels of cytochromes present in the mutant. This mutation may affect some regulatory aspect of ALA formation and renders an ALA‐S of high activity; moreover, this enzyme species seems to be more stable

ISSN:0749-503X    

DOI:10.1002/yea.320090207

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractStrains bearing thevph2mutation are defective in vacuolar acidification. TheVPH2gene was isolated from a genomic DNA library by complementation of the zinc‐sensitive phenotype of the mutant. Deletion analysis localized the complementing activity to a 1·2 kb DNA fragment. Sequence analysis of this fragment revealed the presence of a single open reading frame that encoded a protein of 215 amino acids. Computer analysis indicated that the protein, which has a predicted molecular mass of 25 286 Daltons, has two distinct membrane‐spanning domains. Biochemical studies indicated that strains bearing thevph2mutation have greatly reduced levels of vacuolar proton pumping and ATPase activity and that the nucleotide binding subunits of the multimeric vacuolar H+‐ATPase failed to be correctly targeted to the vacuolar membrane. Thevph2mutant fails to grow on YEP glycerol medium and on media containing 100 mM‐CaCl2or 4 mM‐ZnCl2or buffered to pH 7·5, a phenotype observed in strains carrying deletions in the genes encoding several vacuolar H+‐ATPase subunits. TheVPH2gene is identical to theVMA12gene (T. Stevens and Y. Anraku, personal c

ISSN:0749-503X    

DOI:10.1002/yea.320090208

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0749-503X    

DOI:10.1002/yea.320090209

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe report here the sequence of a 19,482 bp DNA segment of chromosome II ofSaccharomyces cerevisiae. The fragment contains 16 open reading frames (ORFs) covering 74% of the sequence. Four predicted products present homology with known proteins. The ORF YBR1732 exhibits a strong homology to serine hydroxymethyl transferase; the best score is 53·1% identity in 458 amino acids overlap with the serine hydroxymethyl transferase from rabbit liver. YBR1724, which shows homology with riboflavin synthase ofBacillus subtilis, is probably theRIB5gene implied in riboflavine synthesis and mapped in this region. YBR1733 is homologous to rab protein and YBR1728 is presumably a GTPase activating protein

ISSN:0749-503X    

DOI:10.1002/yea.320090210

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe complete sequence of a cytochromecgene fromKluyveromyces lactisincluding its upstream region is reported. Sequence of the translated open reading frame is discussed in terms of cytochromecstructural requirements. Putative regulatory signals in the upstream region are described and compared with reported sequences which modulate the expression of respiratory‐related yeast gene

ISSN:0749-503X    

DOI:10.1002/yea.320090211

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY