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The C-terminal substrate binding domain of LysR-type transcriptional regulator, CbnR, involved in the chlorocatechol catabolism, contains the type 2 periplasmic binding fold. This CD represents the substrate binding domain of LysR-type regulator CbnR which is involved in the regulation of chlorocatechol breakdown. The chlorocatechol-degradative pathway is often found in bacteria that can use chlorinated aromatic compounds as carbon and energy sources. CbnR is found in the 3-chlorobenzoate degradative bacterium Ralstonia eutropha NH9 and forms a tetramer. CbnR activates the expression of the cbnABCD genes, which are responsible for the degradation of chlorocatechol converted from 3-chlorobenzoate and are transcribed divergently from cbnR. The structural topology of this substrate-binding domain is most similar to that of 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.",