Secondary structure of Streptococcus downei GTF-I glucansucrase

Multiple sequence alignment and structure prediction of glucansucrases prod uced by oral streptococci and Leuconostoc mesenteroides showed that all hav e common structural features, with three major domains. There is no conserv ation of primary sequence or structure in the N-terminal variable region. S equence-based structure prediction combined with circular dichroism spectru m analysis of purified truncated forms of Streptococcus downei GTF-I reveal ed that the core catalytic region has a defined structure consistent with t he proposed (alpha/beta)(8)-barrel structure. The C-terminal domain is a mi xed structure with significant amounts of beta-sheet and random-coil. This information contributes to the development of our understanding of structur e-function relationships in glucansucrases. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights r eserved.