Function and structure of Streptococus sobrinus glucosyltransferase responsible for water-soluble glucan synthesis

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Streptococcus cricetus has four kinds of glucosyltransferase (GTFs), i.e.GTF-I,GTF-S,GTF-SI and GTF-T.These enzymes co-operatively synthesize adhesive water-insoluble glucan from sucrose, which contributes firm adherence of growing organisms to smooth dental surfaces.In this study, the genes encoding glucosyltransferase reponsible for water-soluble glucan synthesis (GTF-S and GTF-T) of S.cricetus HS-6 were cloned. THe sequence of GTF-S genes from S.cricetus and S.downei were compered and show a high degree of homology. There is a 73.9% homology of nucleotides in the genes, and 77.4% homology of amino acids in the deduced protein sequences. In comparison of GTF-T genes with S.cricetus and S.sobrinus, there is 79.7% homology in the genes, and 83.5% homology in the deduced protein sequences.The availability of recombinant E.coli carrying the these genes will greatly facilitate purification of the enzymes for biochemical studies.