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Crystal structure of the C-terminal domain of Streptococcus gordonii surface protein SspB
Structural highlights
FunctionSSPB_STRGN May bind sialic acid residues of salivary agglutinin (SAG) in a calcium-dependent reaction. The interaction of SAG with its receptor in various oral streptococci modulate bacterial colonization of oral tissue and is associated with reduced levels of dental caries. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedStreptococcus gordonii is a primary colonizer and is involved in the formation of dental plaque. This bacterium expresses several surface proteins. One of them is the adhesin SspB, which is a member of the Antigen I/II family of proteins. SspB is a large multi-domain protein that has interactions with surface molecules on other bacteria and on host cells, and is thus a key factor in the formation of biofilms. Here, we report the crystal structure of a truncated form of the SspB C-terminal domain, solved by single-wavelength anomalous dispersion to 1.5 A resolution. The structure represents the first of a C-terminal domain from a streptococcal Antigen I/II protein and is comprised of two structurally related beta-sandwich domains, C2 and C3, both with a Ca(2+) bound in equivalent positions. In each of the domains, a covalent isopeptide bond is observed between a lysine and an asparagine, a feature that is believed to be a common stabilization mechanism in Gram-positive surface proteins. S. gordonii biofilms contain attachment sites for the periodontal pathogen Porphyromonas gingivalis and the SspB C-terminal domain has been shown to have one such recognition motif, the SspB adherence region. The motif protrudes from the protein, and serves as a handle for attachment. The structure suggests several additional putative binding surfaces, and other binding clefts may be created when the full-length protein is folded. Two intramolecular isopeptide bonds are identified in the crystal structure of the Streptococcus gordonii SspB C-terminal domain.,Forsgren N, Lamont RJ, Persson K J Mol Biol. 2010 Apr 2;397(3):740-51. Epub 2010 Feb 4. PMID:20138058[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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