Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order for a yeast strain to ferment maltose it must contain any one of the five dominant MAL loci. Each dominant MAL locus thus far analyzed contains three genes: GENE 1, encoding maltose permease, GENE 2 encoding maltase and GENE 3 encoding a positive trans-acting regulatory protein. In addition to these dominant MAL loci, several naturally occurring, partially functional alleles of MAL1 and MAL3 have been identified. Here, we present genetic and molecular analysis of the three partially functional alleles of MAL1: the MAL1p allele which can express only the MAL activator; the MAL1 g allele which can express both a maltose permease and maltase; and the mal1(0) allele which can express only maltase. Based on our results, we propose that the MAL1p, MAL1g and mal1(0) alleles evolved from the dominant MAL1 locus by a series of rearrangements and/or deletions of this yeast telomere-associated locus as well as by other mutagenic processes of gene inactivation. One surprising finding is that the MAL1g-encoded maltose permease exhibits little sequence homology to the MAL1-encoded maltose permease though they appear to be functionally homologous.
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PMID:The naturally occurring alleles of MAL1 in Saccharomyces species evolved by various mutagenic processes including chromosomal rearrangement. 285 83

We have physically and functionally identified three genes at the MAL6 locus of Saccharomyces carlsbergensis. Using multicopy yeast plasmid vectors, we have subcloned various segments of the entire MAL6 locus. The functional characterization of the MAL6 subcloned regions was determined by (1) analyzing biochemically the levels of MAL-encoded proteins (maltase [alpha-D-glucosidase, E.C. 3.2.1.20] and maltose transport protein) in cells transformed with various MAL6 subclones, and (2) testing the ability of the subclones to complement the maltose fermentation defects of well characterized Mal- mutants in the highly homologous MAL1 locus. The physical homology between MAL6 and MAL1 is in part demonstrated by the gene disruption of MAL1 using subcloned MAL6 DNA sequences. The results demonstrate that the MAL6 locus is a complex of at least three genes: MAL6R, MAL6T and MAL6S. These genes specify, respectively, a regulatory function, a maltose transport activity (presumably the maltose permease) and the structural gene for maltase. The functional organization of the MAL6 locus is thus identical to that which we had previously determined by mutational analysis for the MAL1 locus.
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PMID:Organization of the MAL loci of Saccharomyces. Physical identification and functional characterization of three genes at the MAL6 locus. 299 4

We describe the isolation of a 22.6-kilobase fragment of DNA containing the MAL1 locus of Saccharomyces cerevisiae. Our results demonstrate that the MAL1 locus, like the MAL6 locus, is a complex locus containing three genes. These genes were organized similarly to their MAL6 counterparts. We refer to them as MAL11, MAL12, and MAL13 and show that they are functionally homologous to the MAL61 (encoding maltose permease), MAL62 (encoding maltase), and MAL63 (encoding the positive regulator) genes of the MAL6 locus. Transcription from each of the three genes was analyzed in a strain carrying the undisrupted MAL1 locus and in strains carrying single disruptions in each of the MAL1 genes. The MAL1 and MAL1 loci were found to be highly sequence homologous and conserved throughout the region containing these three genes. The strain used to isolate the MAL1 locus also carried the tightly linked SUC1 gene. The SUC1 gene was found to be located on the same 22.6-kilobase fragment containing the MAL1 locus and 5 kilobases from the 3' end of the MAL12 gene. The meaning of these results with regard to the mechanism of regulation of maltose fermentation is discussed.
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PMID:Structural and functional analysis of the MAL1 locus of Saccharomyces cerevisiae. 302 17

Genetic analysis of the MAL6 locus has previously yielded mal6 mutants which fall into a single complementation group and which are noninducible for maltase and maltose permease. However, the strains used in these studies contained additional partially functional copies of MAL1 (referred to as MAL1g) and MAL3 (referred to as MAL3g). Using a strain lacking MALg genes, we have isolated two classes of mutants and these classes correspond to mutations in MAL63 and MAL61, two genes of the MAL6 complex. Disruptions of MAL63 are noninducible for maltase and maltose permease and for their corresponding mRNAs. The mal6 mutants are shown to map to MAL63. Inducer exclusion as a cause of the noninducible phenotype of the mal63 mutations has been eliminated by constructing a mal63 mutant in a strain constitutive for maltose permease; the strain remains noninducible. These results rigorously demonstrate that MAL63 is a regulatory gene which plays a positive role in the regulation of maltose fermentation.
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PMID:MAL63 codes for a positive regulator of maltose fermentation in Saccharomyces cerevisiae. 305 30

Both the MAL1 and MAL6 loci in Saccharomyces strains have been shown by functional and structural studies to comprise a cluster of at least three genes necessary for maltose utilization. They include regulatory, maltose transport and maltase genes designated MALR, MALT and MALS, respectively. Subclones of each gene derived from the MAL6 locus were inserted into the multicopy shuttle plasmid YEp13, introduced into MAL1 and mal1 strains and the effects of altered gene dosage of each gene, or a combination of them, on MAL gene expression investigated. MAL1 strains transformed with a plasmid carrying the MAL6S gene showed coordinate four to five fold increases in both maltase enzyme activity and its mRNA, whereas no increase in maltose transport activity or of MALT mRNA was observed when MAL6T was present on multicopy plasmids. The presence of the MAL6R gene on a multicopy plasmid led to greatly increased transcription of both inducible and constitutive mRNAs with homology to the regulatory gene; it also gave rise to two fold increases in both induced maltase mRNA levels and enzyme activity, but only in the presence of maltose. However, it had no apparent effect on the accumulation of MALT mRNA. Finally, the induction kinetics of plasmid-borne and chromosomal MALS and MALT gene expression were examined under conditions of altered gene dosage of the MAL6 regulatory and structural genes. The results of these experiments indicate that MALR encodes a trans-acting positive activator that requires maltose for induction of MALS and MALT transcription even when the regulatory gene is present on a multicopy plasmid. Maltose transport can be a rate-limiting factor in MAL gene expression, at least in the early stages of induction. The regulation of the MALS and MALT genes, whose activities are coordinately induced in MAL1 strains by maltose, may in fact exhibit some important differences.
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PMID:Regulation of MAL gene expression in yeast: gene dosage effects. 332 27

Saccharomyces yeast strains able to ferment maltose carry at least one member of a family of MAL loci: MAL1, MAL2, MAL3, MAL4, and MAL6. The MAL6 locus has been cloned and shown to be a cluster of at least three transcribed regions, all of which are required for maltose fermentation. Transcription at two of these genes, MAL61 and MAL62, is both induced by maltose and repressed by glucose. The third gene, MAL63, appears to encode a regulatory product controlling maltose fermentation. In this report, we demonstrate that the MAL62 gene is the structural gene coding for the enzyme maltase. Strain 332-5A is a maltose fermenter of the genotype MAL6 mal1(0). Integrative disruption of the MAL62 gene of the MAL6 locus produces a strain which is still capable of fermenting maltose, but which synthesizes a more heat-labile form of maltase than the undisrupted strain. Synthesis of this more heat-labile maltase was shown to be linked to the mal1(0) locus present in the strain. Integrative disruption of both the MAL62 gene and the MAL62-homologous sequence present at the mal1(0) locus produces a nonfermenter which is unable to synthesize maltase. These results identify MAL62 as the maltase structural gene.
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PMID:Identification of the structural gene encoding maltase within the MAL6 locus of Saccharomyces carlsbergensis. 390 89

Maltose fermentation in Saccharomyces spp. requires the presence of any one of five unlinked genes: MAL1, MAL2, MAL3, MAL4, or MAL6. Although the genes are functionally equivalent, their natures and relationships to each other are not known. At least three proteins are necessary for maltose fermentation: maltase, maltose permease, and a regulatory protein. The MAL genes may code for one or more of these proteins. Recently a DNA fragment containing a maltase structural gene has been cloned from a MAL6 strain, CB11, to produce plasmid pMAL9-26. We have conducted genetic and physical analyses of strain CB11. The genetic analysis has demonstrated the presence of two cryptic MAL genes in CB11, MAL1g and MAL3g (linked to MAL1 and to MAL3, respectively), in addition to the MAL6 locus. The physical analysis, which used a subclone of plasmid pMAL9-26 as a probe, detected three HindIII genomic fragments with homology to the probe. Each fragment was shown to be linked to one of the MAL loci genetically demonstrated to be present in CB11. Our results indicate that the cloned maltase structural gene in plasmid pMAL9-26 is linked to MAL6. Since the MAL6 locus has previously been shown to contain a regulatory gene, the MAL6 locus must be a complex locus containing at least two of the factors needed for maltose fermentation: the structural gene for maltase and the maltase regulatory protein. The absence of other fragments which hybridize to the MAL6-derived probe shows that either MAL2 and MAL4 are not related to MAL6, or the DNA corresponding to these genes is absent from the MAL6 strain CB11.
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PMID:Repeated family of genes controlling maltose fermentation in Saccharomyces carlsbergensis. 634 55

Each of at least five unlinked MAL loci (MAL1 through MAL4 and MAL6) on the yeast genome controls the ability to synthesize an inducible alpha-D-glucosidase (maltase). A subcloned fragment of the coding sequence of the MAL6 maltase structural gene was used as a hybridization probe to investigate the physical structure of the family of MAL structural genes in the genomes of different Saccharomyces strains. MAL+ strains, each carrying a genetically defined MAL locus, were crossed with a MAL- strain and the segregation behavior of the functional locus and of sequences complementary to the maltase structural gene at that locus analyzed. The maltase structural gene sequences of each MaL locus were detected by Southern blot hybridization using BamH1 digests of genomic DNA of the meiotic products. This restriction enzyme was previously shown to cleave outside the confines of the MAL 6 locus. The results of such experiments indicate that each MAL locus encompasses at least one maltase structural gene sequence homologous to that of MAL6, that yeast strains that lack functional MAL loci may or may not contain the corresponding maltase structural gene sequence, that the MAL1 maltase structural gene sequence or one of its alleles can be detected in all laboratory yeast strains examined and that each MAL locus can be identified as a characteristic BamH1 fragment of genomic DNA which includes a maltase structural gene. Yeast strains vary in the number of maltase structural gene sequences that they carry. By using the approach described in this report, the ones corresponding to the different functional MAL loci and residing within a BamH1 generated restriction fragment can be identified.
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PMID:Identification and physical characterization of yeast maltase structural genes. 635 59

Fermentation of maltose by Saccharomyces strains depends on the presence of any one of five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 or MAL6). Earlier mutational analyses of MAL2 and MAL6 containing strains have identified a single complementation group at each of these two loci. However complementation analysis between naturally occurring Mal- Saccharomyces strains isolated from the wild demonstrated the presence of two complementation groups (designated MALp and MALg) at the MAL1, MAL3 and MAL6 loci. The available evidence suggests that the MALp gene is functionally equivalent to the complementation group identified by mutational analysis at the MAL6 locus and that this gene encodes a protein involved in the regulation of the coordinate induction of both maltase and maltose permease synthesis. In this paper we report the isolation, in a well characterized MAL1 strain, of 47 mutants unable to ferment maltose. All the mutants, with one exception, map at the MAL1 locus. These mal1 mutants, except for one, are recessive to MAL1 and fall into two major complementation groups. Evidence is presented that these two classes of mutants identify both a gene involved in the regulation of maltose identify both a gene involved in the regulation of maltose fermentation (MAL1R) and a gene involved in maltose transport (MAL1T). We also report here the isolation of a temperature sensitive maltose nonfermenting mutant mapping at the MAL1 locus identifying a third gene (MAL1S) at this locus. The maltase synthesized by this mutant, when assayed in cell-free extracts, is significantly more thermolabile than the wild type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mutational analysis of the MAL1 locus of Saccharomyces: identification and functional characterization of three genes. 638 96

Inbred haploid strains of Saccharomyces cerevisiae carrying MAL1, MAL2 or MAL6 in a common background have been crossed to each other and to strains carrying no active MAL loci. The kinetics of maltase induction and the induced maltase levels have been examined in the inbred strains and in haploid segregants of the crosses. Differences have been found in the kinetics of induction and induced maltase levels that segregate with the different MAL loci. In the strains tested, the relative rates of maltase induction were MAL2 greater than MAL6 much greater than MAL1; the relative induced maltase levels were MAL2 greater than MAL6 similar to MAL1. These results indicate that MAL1, MAL2 and MAL6 are (or include) regulatory genes that control the accumulation of the enzymes of maltose fermentation.
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PMID:The effects of three different mal loci on the regulation of maltase synthesis in yeast. 703 38


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