2r4t

Publication Abstract from PubMed

Escherichia coli glycogen synthase (EcGS, EC 2.4.1.21) is a retaining glycosyltransferase (GT) that transfers glucose from adenosine diphosphate glucose to a glucan chain acceptor with retention of configuration at the anomeric carbon. EcGS belongs to the GT-B structural superfamily. Here we report several EcGS x-ray structures that together shed considerable light on the structure and function of these enzymes. The structure of the wild-type enzyme bound to ADP and glucose revealed a 15.2 degrees overall domain-domain closure and provided for the first time the structure of the catalytically active, closed conformation of a glycogen synthase. The main chain carbonyl group of His-161, Arg-300, and Lys-305 are suggested by the structure to act as critical catalytic residues in the transglycosylation. Glu-377, previously thought to be catalytic is found on the alpha-face of the glucose and plays an electrostatic role in the active site and as a glucose ring locator. This is also consistent with the structure of the EcGS(E377A)-ADP-HEPPSO complex where the glucose moiety is either absent or disordered in the active site.

The crystal structures of the open and catalytically competent closed conformation of Escherichia coli glycogen synthase.,Sheng F, Jia X, Yep A, Preiss J, Geiger JH J Biol Chem. 2009 Jun 26;284(26):17796-807. Epub 2009 Feb 25. PMID:19244233^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.