Cloning of the Streptococcus mutans gene encoding glucan binding protein Band analysis of genetic diversity and protein production in clinical isolates

Streptococcus mutans, the primary etiological agent of dental caries, produ ces several activities that promote its accumulation within the dental biof ilm. These include glucosyltransferases, their glucan products, and protein s that bind glucan. At least three glucan binding proteins have been identi fied, and GbpB, the protein characterized in this study, appears to be nove l. The gbpB gene was cloned and the predicted protein sequence contained se veral unusual features and shared extensive homology with a putative peptid oglycan hydrolase from group B streptococcus. Examination of gbpB genes fro m clinical isolates of S. mutans revealed that DNA polymorphisms, and hence amino acid changes, were limited to the central region of the gene, sugges ting functional conservation within the amino and carboxy termini of the pr otein. The GbpB produced by clinical isolates and laboratory strains showed various distributions between cells and culture medium, and amounts of pro tein produced by individual strains correlated positively with their abilit y to grow as biofilms in an in vitro assay.