The substrate binding domain of LysR-type transcriptional regulator GltC, which activates gltA expression of glutamate synthase operon, contains type 2 periplasmic binding fold.
GltC, a member of the LysR family of bacterial transcriptional factors, activates the expression of gltA gene of glutamate synthase operon and is essential for cell growth in the absence of glutamate. Glutamate synthase is a heterodimeric protein that encoded by gltA and gltB, whose expression is subject to nutritional regulation. GltC also negatively auto-regulates its own expression. This substrate-binding domain has strong homology to the type 2 periplasmic binding proteins (PBP2), which are responsible for the uptake of a variety of substrates such as phosphate, sulfate, polysaccharides, lysine/arginine/ornithine, and histidine. The PBP2 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 cytoplasmically located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis.
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