title: Identification of a Streptococcus gordonii SspB domain that mediates adhesion to Porphyromonas gingivalis.
abstract: Porphyromonas gingivalis, a primary pathogen in adult periodontitis, may establish itself in the oral cavity by adhering to early plaque bacteria such as Streptococcus gordonii. Our previous studies (R. J. Lamont et al., Microbiology 140:867-872, 1994) suggested that this interaction is mediated by the SspB polypeptide, a member of the antigen I/II family of streptococcal surface proteins. S. gordonii was recently shown to express a second Ssp polypeptide (SspA) that resembles SspB and the structurally homologous antigen I/II polypeptide (Pac) of Streptococcus mutans. To determine if all of these related antigen I/II proteins interacted with P. gingivalis, SspA, SspB, and Pac were tested for adhesion to P. gingivalis cells. Both of the S. gordonii Ssp proteins bound labeled target cells, whereas the S. mutans Pac polypeptide did not, suggesting that antigen I/II-mediated binding of P. gingivalis by streptococci may be species specific. To investigate the molecular basis for this functional difference, the P. gingivalis binding domain of SspB was mapped. The binding properties of a family of truncated SspB polypeptides lacking C-terminal sequences were determined. In addition, the lack of binding activity exhibited by the Pac protein was exploited to construct and analyze chimeric SspB-Pac polypeptides. Both approaches revealed that the region defined by residues 1167 to 1250 of SspB was essential for P. gingivalis binding. This region of SspA and SspB is entirely conserved, consistent with the binding properties determined for these proteins. However, the corresponding region of Pac differs in both the primary sequence and predicted secondary structure, suggesting that the overall structure of this domain may define its functional activity.
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: W
authors.initials: W
authors.lastname: Brooks
authors.forename: D R
authors.initials: DR
authors.lastname: Demuth
authors.forename: S
authors.initials: S
authors.lastname: Gil
authors.forename: R J
authors.initials: RJ
authors.lastname: Lamont
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D037102:Lectins / Q000378:metabolism*; D008562:Membrane Glycoproteins; D009055:Mouth / Q000382:microbiology; D010446:Peptide Fragments / Q000378:metabolism; D010518:Periodontitis / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000472:pathogenicity*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D013291:Streptococcus / Q000472:pathogenicity*; D013329:Structure-Activity Relationship
chemical_list: D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D037102:Lectins; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C055764:S-layer proteins; C082314:SspA protein, bacteria; C068465:salivary agglutinin receptor, Streptocococcus