Redox Switch for the Inhibited State of Yeast Glycogen Synthase Mimics Regulation by Phosphorylation
Autor: | Sulochanadevi Baskaran, Anna A. DePaoli-Roach, Krishna K. Mahalingan, Peter J. Roach, Thomas D. Hurley |
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Rok vydání: | 2016 |
Předmět: |
Models
Molecular Uridine Diphosphate Glucose 0301 basic medicine Saccharomyces cerevisiae Proteins Mutant Glucose-6-Phosphate Saccharomyces cerevisiae Crystallography X-Ray Biochemistry Protein Structure Secondary Article 03 medical and health sciences chemistry.chemical_compound Protein Domains Glycogen branching enzyme Cysteine Phosphorylation Glycogen synthase Cysteine metabolism chemistry.chemical_classification 030102 biochemistry & molecular biology Glycogen biology Enzyme Activation Kinetics Glycogen Synthase 030104 developmental biology Enzyme chemistry Mutation biology.protein Protein Multimerization Crystallization Oxidation-Reduction |
Zdroj: | Biochemistry. 56:179-188 |
ISSN: | 1520-4995 0006-2960 |
Popis: | Glycogen synthase (GS) is the rate limiting enzyme in the synthesis of glycogen. Eukaryotic GS is negatively regulated by covalent phosphorylation and allosterically activated by glucose-6-phosphate (G-6-P). To gain structural insights into the inhibited state of the enzyme, we solved the crystal structure of yGsy2-R589A/R592A to a resolution of 3.3 Å. The double mutant has an activity ratio similar to the phosphorylated enzyme and also retains the ability to be activated by G-6-P. When compared to the 2.88 Å structure of the wild-type G-6-P activated enzyme, the crystal structure of the low-activity mutant showed that the N-terminal domain of the inhibited state is tightly held against the dimer-related interface thereby hindering acceptor access to the catalytic cleft. On the basis of these two structural observations, we developed a reversible redox regulatory feature in yeast GS by substituting cysteine residues for two highly conserved arginine residues. When oxidized, the cysteine mutant enzyme exhibits activity levels similar to the phosphorylated enzyme but cannot be activated by G-6-P. Upon reduction, the cysteine mutant enzyme regains normal activity levels and regulatory response to G-6-P activation. |
Databáze: | OpenAIRE |
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