Substrate binding domain of ABC-type histidine/lysine/arginine/ornithine transporter-like; the type 2 periplasmic-binding protein fold
This group includes uncharacterized periplasmic substrate-binding protein similar to HisJ and LAO proteins which serve as initial receptors in the ABC transport of histidine-, arginine, and lysine-arginine-ornithine amino acids. This group belongs to the type 2 periplasmic-binding fold protein (PBP2) superfamily, whose members are involved in chemotaxis and uptake of nutrients and other small molecules from the extracellular space as a primary receptor. PBP2 typically comprises of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap. After binding their specific ligand with high affinity, they can interact with a cognate membrane transport complex comprised of two integral membrane domains and two receptor cytoplasmically-located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",