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Two glycogen synthase isoforms in Saccharomyces cerevisiae are coded by distinct genes that are differentially
I Farkas1, T A Hardy, M G Goebl
1Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202-5122.
The Journal of Biological Chemistry
|August 25, 1991
Summary
Yeast has two glycogen synthase genes, GSY1 and GSY2. GSY2 is the main enzyme, crucial for glycogen synthesis, especially when nutrients are scarce.
Area of Science:
- Biochemistry
- Molecular Biology
- Yeast Genetics
Background:
- Identified Saccharomyces cerevisiae glycogen synthase gene GSY1 previously.
- GSY1 encodes an 85-kDa polypeptide in purified yeast glycogen synthase.
Purpose of the Study:
- Clone and characterize a second gene, GSY2, encoding another S. cerevisiae glycogen synthase.
- Investigate the roles of GSY1 and GSY2 in glycogen synthesis and cellular glycogen levels.
Main Methods:
- Gene cloning and sequencing of GSY2.
- Gene disruption experiments for GSY1 and GSY2.
- Measurement of glycogen synthase activity in wild-type and mutant strains.
- Analysis of glycogen deposition in disrupted strains.
Main Results:
- GSY2 encodes a 79,963 Da protein with 80% identity to GSY1 product.
- GSY1 disruption retained 85% activity; GSY2 disruption retained 10% activity.
- Disruption of both GSY1 and GSY2 resulted in complete loss of glycogen synthase activity and defective glycogen deposition.
Conclusions:
- Saccharomyces cerevisiae expresses two distinct glycogen synthase genes, GSY1 and GSY2.
- GSY2 is the predominant glycogen synthase, with activity linked to nutrient depletion.
- Both genes are essential for normal glycogen synthesis and deposition in yeast.