Streptococcus gordonii is an important member of the oral flora. This species is also known as a leading cause of infective endocarditis. The bacterial binding to platelets is thought to be a major virulence determinant in the pathogenesis of infective endocarditis. Recently, S. gordonii surface glycoproteins GspB and Hsa have been shown to mediate bacterial binding to platelets via sialic acid moieties on platelet membrane glycoptotein (GP) Ibα. However, the binding specificity of the adhesins has not been completely elucidated. In this study, we revealed that Hsa binds GPIbα via α(2-3) sialyllactosamine [NeuAcα(2-3)Galβ(1-4)GlcNAc] and sialyl-T antigen [NeuAcα(2-3)Galβ(1-3)GalNAc] on the protein, whereas GspB can recognize only sialyl-T antigen. In addition, both proteins were shown to directly bind several salivary proteins including low-molecular-weight salivary mucin MG2 and salivary agglutinin, suggesting the importance of the adhesins for oral bacterial colonization. Since GspB homologues are conserved in several gram-positive bacteria, these proteins may also mediate bacterial binding to host tissues.
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Reference:
- Takamatsu et al. (2005) Mol. Microbiol. 58 : 380-392.
- Takamatsu et al. (2006) Infect. Immun. 74 : 1933-1940.
