Three-dimensional modelling of the catalytic domain of Streptococcus mutans glucosyltransferase GtfB

Glucosyltransferases (GtfB/C/D) of Streptococcus mutans, a pathogen for hum an dental caries, synthesize water-insoluble glucan through the hydrolysis of sucrose. Genetic and biochemical approaches have identified several acti ve sites of these enzymes, but no three-dimensional (3D) structural evidenc e is yet available to elucidate the subdomain arrangement and molecular mec hanism of catalysis. Based on a combined sequence and secondary structure a lignment against known crystal structures of segments from closely related proteins, we propose here the 3D model of an N-terminal domain essential fo r the sucrose binding and splitting in GtfB. A Tim-barrel of (alpha/beta)(8 ) structural characteristics is revealed and the structural correlation for two peptides is described. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.