Structural Insights into the Mechanism for Recognizing Substrate of the Cytochrome P450 Enzyme TxtE

摘要: Thaxtomins, a family of phytotoxins produced by Streptomyces spp., can cause dramatic plant cell hypertrophy and seedling stunting. Thaxtomin A is the dominant form from scabies has demonstrated herbicidal action. TxtE, cytochrome P450 enzyme 87.22, catalyzes direct nitration indolyl moiety L-tryptophan to L-4-nitrotryptophan using nitric oxide, dioxygen NADPH. The crystal structure TxtE was determined at 2.1 resolution described in this work. clearly defined substrate access channel observed be classified as 2a, which common bacteria enzymes. continuous hydrogen bond chain active site external solvent observed. Compared with other enzymes, shows unique proton transfer pathway crosses helix I distortion. Polar contacts Arg59, Tyr89, Asn293, Thr296, Glu394 are seen molecular docking analysis, potentially important for recognition binding. After mutating Thr296 or leucine, binding ability lost decreased significantly. Based on mutation results, possible mechanism proposed.