Purification of a novel fibronectin binding protein from 'Granulicatella para-adiacens'

The interaction of microorganisms with fibronectin plays an important role in infective endocarditis. Characterization of fibronectin binding is not sufficient for nutritionally variant streptococci (NVS), which is an important pathogen associated with this disease. In this study, we identified and purified the novel fibronectin binding protein (FBP) by sonication and column chromatography from a ' Granulicatella para-adiacens' strain isolated from the oral cavity of a healthy donor. The purified molecule was located at the top of the gel in SDS-PAGE analysis, and heat treatment in the presence of sodium dodecyl sulfate resulted in its dissociation into smaller molecules. An anti-purified protein antibody was reacted with the topmost component of the sonic extract only from two ' G. para-adiacens' strains in Western blot analyses. Immunofluorescence staining indicated that the protein of interest was located on the cell surface of ' G. para-adiacens', but not on other NVS species. Bacterial adherence to fibronectin was inhibited by the purified FBP preparation. Optimum conditions for fibronectin binding of purified FBP were shown to be an NaCl concentration higher than 150 mM and a pH of c. 7.0. These results provide additional information for the elucidation of fibronectin binding by NVS.