3RT1

Maltodextarn bound activated state form of yeast glycogen synthase isoform 2

Summary for 3RT1

• Entry DOI: 10.2210/pdb3rt1/pdb
• Related: 3NB0
• Related PRD ID: PRD_900009 PRD_900010 PRD_900030
• Descriptor: PROTEIN (Glycogen [starch] synthase isoform 2), alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (7 entities in total)
• Functional Keywords: maltodextarn binding, rossmann fold, glycosyl transferase, glycogen binding, transferase
• Biological source: Saccharomyces cerevisiae (brewer's yeast,lager beer yeast,yeast)
• Total number of polymer chains: 4
• Total formula weight: 334664.22

Authors

Baskaran, S.,Hurley, T.D. (deposition date: 2011-05-02, release date: 2011-08-10, Last modification date: 2024-02-28)

Primary citation

Baskaran, S.,Chikwana, V.M.,Contreras, C.J.,Davis, K.D.,Wilson, W.A.,Depaoli-Roach, A.A.,Roach, P.J.,Hurley, T.D.
Multiple Glycogen-binding Sites in Eukaryotic Glycogen Synthase Are Required for High Catalytic Efficiency toward Glycogen.
J.Biol.Chem., 286:33999-34006, 2011

PubMed Abstract: Glycogen synthase is a rate-limiting enzyme in the biosynthesis of glycogen and has an essential role in glucose homeostasis. The three-dimensional structures of yeast glycogen synthase (Gsy2p) complexed with maltooctaose identified four conserved maltodextrin-binding sites distributed across the surface of the enzyme. Site-1 is positioned on the N-terminal domain, site-2 and site-3 are present on the C-terminal domain, and site-4 is located in an interdomain cleft adjacent to the active site. Mutation of these surface sites decreased glycogen binding and catalytic efficiency toward glycogen. Mutations within site-1 and site-2 reduced the V(max)/S(0.5) for glycogen by 40- and 70-fold, respectively. Combined mutation of site-1 and site-2 decreased the V(max)/S(0.5) for glycogen by >3000-fold. Consistent with the in vitro data, glycogen accumulation in glycogen synthase-deficient yeast cells (Δgsy1-gsy2) transformed with the site-1, site-2, combined site-1/site-2, or site-4 mutant form of Gsy2p was decreased by up to 40-fold. In contrast to the glycogen results, the ability to utilize maltooctaose as an in vitro substrate was unaffected in the site-2 mutant, moderately affected in the site-1 mutant, and almost completely abolished in the site-4 mutant. These data show that the ability to utilize maltooctaose as a substrate can be independent of the ability to utilize glycogen. Our data support the hypothesis that site-1 and site-2 provide a "toehold mechanism," keeping glycogen synthase tightly associated with the glycogen particle, whereas site-4 is more closely associated with positioning of the nonreducing end during catalysis.

PubMed: 21835915
DOI: 10.1074/jbc.M111.264531

Experimental method

X-RAY DIFFRACTION (2.8 Å)