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.

Microbial interactions in building of communities

“…P. gingivalis does not interact with all AgI/II family members, despite conservation in primary amino acid sequences and secondary structure (Brady et al, 2010). For example, P. gingivalis does not recognize SpaP of S. mutans (Brooks et al, 1997). The precise region of SspA/B involved in binding P. gingivalis was determined by examining a series of truncated SspB polypeptides and chimeric proteins consisting of portions of SspB and SpaP.…”

Streptococcus gordoniiDL1 adhesin SspB V‐region mediates coaggregation via receptor polysaccharide of Actinomyces oris T14V

“…The SspB protein has multiple binding functions and a new activity directly involved in coaggregation of early colonizers has been characterized here. The SspB protein is now known to have at least three different microbial partners, A. oris, P. gingivalis (Brooks et al, 1997) and C. albicans (Silverman et al, 2010), in addition to recognizing gp340, fibronectin (Nobbs et al, 2007) and collagen (Love et al, 1997). The interaction of SspB with A. oris seems to be located to the V-region.…”

“…The interaction of SspB with A. oris seems to be located to the V-region. On the other hand, interaction of SspB with P. gingivalis is located in the C-domain, downstream from the P-rich repeats (Brooks et al, 1997). The discrete locations of various binding sites on SspB for interaction with different microorganisms, and host molecules, therefore ensures maximum protein functionality.…”

“…The oral (viridans) streptococci express antigen I/II (AgI/II) family polypeptide adhesins (Brady et al, 2010). These proteins are involved in binding a wide range of host receptors , mediate biofilm formation (Pecharki et al, 2005), and may promote coaggregation with oral microbial partners (Brooks et al, 1997;Egland et al, 2001). Streptococcus gordonii expresses two AgI/II family proteins on its surface, designated SspA and SspB, encoded by tandemly arranged genes on the S. gordonii DL1 chromosome (Demuth et al, 1996).…”

Identification of functional domains of the minor fimbrial antigen involved in the interaction of Porphyromonas gingivalis with oral streptococci

“…The primary niche for P. gingivalis is the subgingival pocket but the organism also adheres efficiently to supragingival bacteria such as various commensal streptococci (Brooks, Demuth, Gil, & Lamont, 1997;Demuth, Irvine, Costerton, Cook, & Lamont, 2001;Lamont, Hersey, & Rosan, 1992). Indeed, adherence to streptococci can modulate the pathogenic potential of P. gingivalis (Daep, Novak, Lamont, & Demuth, 2011;Kuboniwa et al, 2017;Kuboniwa & Lamont, 2010) and may also be important for the initial colonization of the oral cavity by the organism.…”