Four critical aspartic acid residues potentially involved in the catalyticmechanism of Escherichia coli K-12 WaaR

Escherichia coli K-12 WaaR is a non-processive alpha-1,2 glucosyltransferas e, involved in the synthesis of the R-core of lipopolysaccharide. WaaR poss esses the four conserved structural regions I, II, III and IV, each presuma bly involved in the mechanistic function in catalysis. Regions I and III co ntain the pair of strictly conserved Asp residues. Asp-129, 131 (region I) and 215, 217 (region III) of WaaR were individually converted to Asn by the site-directed mutagenesis of the waaR gene. All mutated enzymes were inact ive, supporting the model for an a-glycosyl transfer reaction where the pai r of strictly conserved aspartic acid residues in regions I and III play a critical role in the catalytic function. (C) 1999 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V. All rights rese rved.