Functions in inorganic phosphate uptake, although probably not the main uptake protein under phosphate starvation (PubMed:15731097, PubMed:20933472). Binds phosphate; probably able to bind both H(2)PO(4)(-) and HPO(4)(2-) (PubMed:8294447, PubMed:12842040). Part of the ABC transporter complex PstSACB involved in phosphate import (Probable). A host TLR2 agonist (toll-like receptor), shown experimentally for human and mouse (PubMed:1906192, PubMed:19362712). Requires both host TLR1 and TLR2 as coreceptors to elicit host response in mouse (TLR6 may also play a role) neither CD14 or CD36 function as accessory receptors (PubMed:19362712). Protein purified from culture filtrate induces host (human) monocytes to produce TNF-alpha, IL-6 and IL-12 p40 (IL12B) via ERK1/2 (MAPK3 and MAPK1) and p38 MAPK pathways; MEK inhibitors U0126 and PD98059 and p38 inhibitor SB203580 block most cytokine production (PubMed:16622205). Host ERK1/2 and p38 MAPK activation is mediated mainly by TLR2, but also partially by TLR4, and unlike the case for lipoprotein LpqH the protein moiety of PstS1 seems to be the antigenic agent (PubMed:16622205). Greater activation of ERK1/2 and p38 MAPK is seen in patients with active pulmonary tuberculosis than in tuberculin-negative patients (PubMed:16622205). Induces apoptosis when incubated with human monocyte-derived macrophages via TLR2 (PubMed:19140873). Protein purified from culture filtrate acts via TLR2 and TLR4 to induce host macrophage (shown for mouse) endoplasmic reticulum stress-mediated apoptosis via MAPK (at least JNK), C-C motif chemokine 2 (MCP-1, Ccl2) and ZC3H12 endoribonucleases (MCPIP, Zc3h12) (PubMed:25544271). Functions as an adhesin, binds to human and mouse macrophages via mannose residues, binds to the mouse macrophage mannose receptor (possibly Mrc1) and mediates bacterial phagocytosis (PubMed:25359607). The ABC transporter complex is composed of two ATP-binding proteins (PstB), two transmembrane proteins (PstC and PstA) and a solute-binding protein (PstS). A soluble cell wall-associated protein (PubMed:10426995). Also found in culture filtrate in increasing quantities during growth (PubMed:1906192, PubMed:16622205). Transcription slightly induced by phosphate starvation, part of the pstB3-pstS2-pstC1-pstA2 operon (PubMed:20933472). Strongly induced by phosphate starvation (at protein level) (PubMed:1612766). Also shown to be only slightly induced by phosphate starvation; results may depend on growth media (at protein level) (PubMed:20933472). Glycosylated, probably with mannose residues; treatment with alpha-D-mannosidase abolishes its interaction with concanavalin A. No growth phenotype in phosphate-rich medium (3.6 mM Pi), decreased phosphate uptake in phosphate-depleted medium (PubMed:15731097). Grows faster than wild-type in restricted (Sauton) phosphate-free medium, even after nutrient starvation (PubMed:20933472). Decreased growth in infected BALB/c and C57BL/6 mice for up to 5 months after infection (PubMed:15731097). When used as a vaccine has immunostimulatory properties; it stimulates the differentiation of unrelated antigen memory CD4+ T-cells to produce IFN-gamma, IL-17 and IL-22. Belongs to the PstS family.