Periplasmic substrate binding domain of ABC-type transporter specific to alanine; the type 2 periplasmic binding protein.
This periplasmic substrate component serves as an initial receptor in the ABC transport of glutamine in eubacteria and archaea. After binding the alanine with high affinity, this domain 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. This alanine specific domain belong to the PBP2 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.",