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The C-terminal substrate-domain of LysR-type transcriptional regulator, OccR, involved in the catabolism of octopine, contains the type 2 periplasmic binding fold. This CD includes the C-terminal substrate-domain of LysR-type transcriptional regulator OccR, which is involved in the catabolism of octopine. Opines are low molecular weight compounds found in plant crown gall tumors produced by the parasitic bacterium Agrobacterium. There are at least 30 different opines identified so far. Opines are utilized by tumor-colonizing bacteria as a source of carbon, nitrogen, and energy. In Agrobacterium tumefaciens, OccR protein activates the occQ operon of the Ti plasmid in response to octopine. This operon encodes proteins required for the uptake and catabolism of octopine, an arginine derivative. The occ operon also encodes the TraR protein, which is a quorum-sensing transcriptional regulator of the Ti plasmid tra regulon. This substrate-binding domain shows significant 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",