Mediates binding to human platelets, possibly through a receptor-ligand interaction. Probably associated with virulence in endovascular infection (PubMed:15784571). Plays a positive role in biofilm formation, possibly by self-association via the non-repeat region (NRR or binding region, BR) (PubMed:20714350). Binds to and plays a role in human lung epithelial cell invasion via the L-lectin module of its NRR domain; N-acetylneuraminic acid (Neu5Ac) inhibits binding. Treatment of host cells with neuraminidase decreases adherence of S.aureus cells, suggesting SraP recognizes a host terminal Neu5Ac moiety as a receptor (PubMed:24901708). Primarily exported by the accessory SecA2/SecY2 protein translocation apparatus (PubMed:18621893). Distributed in a discrete, punctate pattern with up to 3 loci per cell over the surface (PubMed:18800056). Anchored to the cell wall by sortase A (Probable). Most highly expressed in the transient phase between exponential and stationary growth. A further 2-fold induction occurs in secG or secG/secY2 disruption mutants. The non-repeat region (NRR, also called binding region, BR) binds to whole cell lysates of wild-type but not bacteria deleted of this gene; it also recognizes whole cell lysates of S.gordonii strain M99 probably via GspB, but not lysates of S.pneumoniae TIGR4 (PubMed:20714350). The NRR is acidic, with a predicted pI of 5.69 in strain ISP479C (PubMed:19202081). The NRR has 4 discrete modules that align end-to-end to form a slightly bent rod. The first is an L-lectin module which binds 1 Ca(2+) ion and N-acetylneuraminic acid (Neu5Ac), and mediates adhesion to human lung epithelial cells (A549 cell line), probably via sialylated receptors. Neu5Ac inhibits binding of A549 cells by the NRR domain. The second beta-grasp module adopts a ubiquitin-like beta-grasp fold which resembles the Ig-binding superfamily, while the 2 other modules resemble cadherins; the cadherin-like modules each bind a Ca(2+). Ca(2+) binding rigidifies the cadherin-like modules and extends the molecule (PubMed:24901708). Proteolytically cleaved by a metalloprotease. Glycosylated (PubMed:15784571). It is probable that most of the Ser residues in SSR1 and SSR2 are O-GlcNAcylated. Sequential glycosylation by sugar transferases are able to generate complex sugar polymorphisms (By similarity). Decrease in early biofilm formation (PubMed:20714350). About 40% reduction in adhesion to human lung epithelial cells and about 50% reduction in host cell invasion. No significant reduction in biofilm formation or bacterial aggregation (PubMed:24901708). Belongs to the serine-rich repeat protein (SRRP) family.