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The intact gtfC gene from Streptococcus mutans GS-5 was isolated in Escherichia coli in plasmid vector pUC18. The glucosyltransferase activity expressed by the gene synthesized both low-molecular-weight water-soluble glucan and insoluble glucan in a primer-independent manner. Purification of the enzyme by procedures that minimize proteolytic digestion yielded a purified preparation with a molecular weight of 140,000. Insertional inactivation of the gtfC gene with a streptococcal erythromycin resistance gene fragment followed by transformation of strain GS-5 suggested that the gtfC gene product was required for sucrose-dependent colonization in vitro. In addition, evidence for the presence of a third gtf gene coding for soluble glucan synthesis was obtained following the construction of mutants containing deletions of both the gtfB and gtfC genes.
Hanada et al. (Mon,) studied this question.