DNA sequence of the glucosyltransferase gene of serotype d Streptococcus sobrinus.

A glucosyltransferase (GTF) gene was cloned into Escherichia coli from serotype d Streptococcus sobrinus OMZ176. Transformed E. coli strain MI expressed water-insoluble glucan synthesizing activity. Restriction enzyme map of pGT31 extracted from MI shows that the enzyme gene exists in the 6.4-KB PstI-fragment inserted into pBR322 vector. DNA sequence analysis indicates that a single ORF (530-5,300) is located in the PstI-fragment. The putative amino-acid composition (1,590 residues) resembles those of other GTF-I enzymes obtained from serotype g S. sobrinus and serotype h Streptococcus downei. However, at the same positions of the sequence, 18 and 142 amino-acid residues are different between serotype d and g, and serotype d and h GTF-I enzymes, respectively. The differences between serotype d and h GTF-Is are distributed in N and C-terminal regions.