Conformational plasticity of glycogenin and its maltosaccharide substrate during glycogen biogenesis.

ABSTRACT: Glycogenin initiates the synthesis of a maltosaccharide chain covalently attached to itself on Tyr195 via a stepwise glucosylation reaction, priming glycogen synthesis. We have captured crystallographic snapshots of human glycogenin during its reaction cycle, revealing a dynamic conformational switch between ground and active states mediated by the sugar donor UDP-glucose. This switch includes the ordering of a polypeptide stretch containing Tyr195, and major movement of an approximately 30-residue "lid" segment covering the active site. The rearranged lid guides the nascent maltosaccharide chain into the active site in either an intra- or intersubunit mode dependent upon chain length and steric factors and positions the donor and acceptor sugar groups for catalysis. The Thr83Met mutation,

SUBMITTER: Chaikuad A 

PROVIDER: S-EPMC3248551 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature