Secondary structure of Streptococcus downei GTF-1 glucansucrase.

Multiple sequence alignment and structure prediction of glucansucrases produced by oral streptococci and Leuconostoc mesenteroides showed that all have common structural features, with three major domains. There is no conservation of primary sequence or structure in the N-terminal variable region. Sequence-based structure prediction combined with circular dichroism spectrum analysis of purified truncated forms of Streptococcus downei GTF-I revealed that the core catalytic region has a defined structure consistent with the proposed (alpha/beta)8-barrel structure. The C-terminal domain is a mixed structure with significant amounts of beta-sheet and random-coil. This information contributes to the development of our understanding of structure-function relationships in glucansucrases.