Genetic, structural and functional analysis of the alpha-glucoside transporter encoded by MAL11-2.
Item
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Title
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Genetic, structural and functional analysis of the alpha-glucoside transporter encoded by MAL11-2.
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Identifier
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AAI9207062
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identifier
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9207062
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Creator
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Cotty, Francis E.
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Contributor
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Adviser: Corinne Michels
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Biology, Genetics
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Abstract
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The determining factor in {dollar}\alpha{dollar}-glucoside fermentation by Saccharomyces is the transport of this class of sugars into the cell. Different Saccharomyces strains ferment various {dollar}\alpha{dollar}-glucosides including maltose, turanose, isomaltose, maltotriose and sucrose. Previous work in our laboratory has characterized the maltose permease encoded by the MAL1 and MAL6 loci. The MAL1g allele is a naturally occurring partially functional variant of MAL1 proposed to be the result of a chromosomal rearrangement of the right telomere region of chromosome VII. Based upon restriction endonuclease mapping and Southern analysis, the genes encoding maltose permease at MAL1 and MAL1g share no sequence homology. In this work we present a structural and functional characterization of the newly identified maltose permease encoded by the MAL1g allele of the MAL1 locus of Saccharomyces cerevisiae, referred to as MAL11-2. MAL11-2 encodes a highly hydrophobic proposed integral membrane protein with considerable structural homology to the MAL61 encoded high-affinity maltose transporter, as well as to the SNF3, HXT1 and HXT2 encoded high affinity glucose transporters from Saccharomyces, and several transporters from a variety of organisms considered to be members of the sugar transporter superfamily. The MAL11-2 transporter is a high-affinity proton symporter with a Km for maltose of 4 to 5 mM. The sequence of the upstream region of the MAL1g allele is presented and compared to that of the MAL6 locus. The 315 base pairs immediately upstream of MAL11-2 show no significant homology to the MAL6 locus. Starting at base pair {dollar}-{dollar}316 of the MAL1g allele the upstream sequence was found to be 100% identical to a 469 base pair region of the MAL61-MAL62 intergenic region containing the UAS{dollar}\sb{lcub}\rm MAL{rcub}{dollar} and extending beyond this into the MAL12 open reading frame. The {dollar}\alpha{dollar}-glucoside specificity of both the MAL11-1 permease and the MAL11-2 permease was determined using plasmid complementation in a genetically defined strain. We found the MAL11-1 maltose transporter is capable of transporting only maltose and turanose, while the MAL11-2 transporter is capable of transporting isomaltose, {dollar}\alpha{dollar}-methylglucoside, maltotriose and palatinose as well as maltose and turanose. Neither is able to transport melezitose or trehalose.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
