Substrate binding domain of putative ABC-type phosphate transporter, a member of the type 2 periplasmic binding fold superfamily.
This subfamily contains uncharacterized phosphate binding domains found in PstS proteins that serve as initial receptors in the ABC transport of phosphate in eubacteria and archaea. After binding the ligand, PstS interacts with a cognate membrane transport complex comprised of two integral membrane domains and two cytoplasmically located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis. The PstS proteins belong to the PBPII superfamily of periplasmic binding proteins that differ in size and ligand specificity, but have similar tertiary structures consisting of two globular subdomains connected by a flexible hinge. They have been shown to bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.
Jiyao W et al.(2023). "The conserved domain database in 2023.",