Protein that allows bacteria to adhere to mammalian host cells. Required for full virulence in mouse infection models when infected intranasally (PubMed:16861665). Required for adhesion to host cells in vitro and for persistence in the lower respiratory tract (PubMed:18507531). Binds host keratin 10 (KRT10) on lung cells which mediates adhesion via the C-terminus of the basic region (BR, residues 273-341); glycosylation of either protein is not required for the interaction (PubMed:19627498). A region in the N-terminus (residues 122-166) self aggregates, contributing to mature biofilm formation (PubMed:20714350). The basic region (BR, residues 187-385) also self aggregates; the BR binds DNA which enhances self aggregation (PubMed:27582320). Binds to human and mouse protein keratin 10 (KRT10). Expressed in exponential phase (at protein level) (PubMed:19627498). About 47-fold induced during biofilm formation versus planktonic (in liquid culture) (PubMed:20714350). Has 3 domains; serine-rich repeat region 1 (SRR1) with 8 imperfect repeats of the sequence SASASAST, a basic region (BR) and serine-rich repeat region 2 (SRR2) with 539 imperfect repeats of the sequence SASASAST (PubMed:11463916) (Probable). A construct expressing SRR1 plus BR binds to a human pneumocyte cell line and prevents bacteria binding to human pneumocyte cells in a dose-dependent manner; antibodies against the same domain partially inhibit host cell adherence (PubMed:18507531). The BR domain mediates host cell adhesion; its deletion prevents binding to unencapsulated host cells. A BR subdomain (residues 273-341) binds to host keratin 10 (KRT10) (PubMed:19627498). The KRT10-binding subdomain forms a compressed barrel, which probably binds the C-terminus of KRT10 via a series of ordered loops (PubMed:24430336). The SRR2 domain probably extends the BR domain outside of the bacterial capsular polysaccharide, possibly by forming a long filament (Probable). The BR domain is also required for PsrP to be able to mediate biofilm formation. A subdomain (residues 122-166) binds to itself, suggesting it may be responsible for self aggregation; self interaction occurs whether the protein is glycosylated or not. The self aggregation and K10 subdomains function independently of each other (PubMed:20714350). Another subfragment of the BR domain (residues 187-385) binds DNA and may be important in self aggregation (PubMed:27582320). The predicted pI of the basic region is 9.91 (PubMed:19202081). Glycosylated (PubMed:19627498). Only truncated substrates greater than 25 residues long are glycosylated by the Gtf1-Gtf2 complex in vitro; only Ser residues have been seen to be glycosylated. Based on electrophoretic mobility it is probable that most of the Ser residues in SSR1 and SSR2 are O-GlcNAcylated (PubMed:24936067). Subsequent glycosylation by up to 7 sugar transferases (Gtf3 and GlyAT, GlyB, GlyD, GlyE, GlyF and GlyG) is able to generate very high sugar polymorphism (PubMed:28246170). Can be cleaved by human furin protease; this fragment contributes to self-aggregation and possibly biofilm formation in vitro. Significantly improved survival of intranasally infected female BALB/cJ mice; bacteria infect nasal tissues normally but do not progress into the blood (PubMed:16861665). Single deletion or deletion of 15 genes (from psrP, SP_1772 to SP_1756, includes the accessory Sec export proteins SecA2 and SecY2) and infection of female BALB/cJ mice, shows the psrP-secY2A2 region is required for lung infection and for infection to progress to blood. Mice infected intraperitoneally with either deletion showed wild-type infection. Both deletions have decreased adherence to lung but not pharynx or brain cells. The psrP-secY2A2 region deletion has no effect on bacterial growth rate, capsule levels, autolysis, or transformation (PubMed:18507531). About 5-fold decreased aggregation of bacteria in infected mouse nasopharynx and lung tissue. In vitro, significantly decreased mature biofilm formation is seen; the large deletion mutant (SP_1772 to SP_1756) is no more affected than the single psrP deletion. Biofilm formation is partially restored by a truncated PsrP (residues 1-734); the BR domain is required for this partial restoration (PubMed:20714350). About 60% decreased biofilm formation, no change in adherence to human lung pneumocytes (PubMed:28456649). Mice vaccinated with residues 72-395 were protected against subsequent infection, suggesting this would be a good candidate for vaccine inclusion. Encoded in RD10, a pathogenicity island with an atypical GC content that is associated with invasive pneumococcal disease. Pathogenicity islands account for greater than half the genomic diversity observed between isolates (PubMed:11463916, PubMed:16861665, PubMed:19627498). The main function of this island seems to be correct synthesis and export of this protein (PubMed:18507531, PubMed:20714350). Normally a commensal colonizing bacteria of the nasopharynx, invasive pneumococcal disease (IPD) is characterized by bacterial spread from the nasopharynx to normally sterile sites such as the lungs, blood, and brain. The young, the elderly and the immunocompromised are at greatest risk for IPD. Belongs to the serine-rich repeat protein (SRRP) family. O-glycosylation sites are annotated in SSR1 only. Residues at similar position are probably glycosylated in SRR2 also. Experimental sites were determined in a synthetic peptide glycosylated by addition of GlcNAc in vitro by GtfA-GtfB; only 13 of 26 possible Ser and no Thr were modified with GlcNAc in this experiment (PubMed:24936067). The GlcNAc residues are subsequently further modified but the positions were not proven in that experiment (PubMed:28246170).