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Substrate binding domain of a putative iron transporter BitB, a member of the type 2 periplasmic binding fold superfamily. The substrate domain of this group shows a high homology to the periplasmic component of ferric iron transporter (Fbp), but its biochemical characterization has not been performed. The periplasmic iron binding protein plays an essential role in the iron uptake pathway of Gram-negative pathogenic bacteria from the Pasteurellaceae and Neisseriaceae families and is critical for survival of these pathogens within the host. After binding iron with high affinity, Fbp interacts with a cognate membrane transport complex comprised of two integral membrane domains and two cytoplasmically located ATPase. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis. The ferric iron-binding proteins 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.",