Crystallization and structural analysis of binary complex of P450 electron donor and its electron transfer mechanism

点击翻译按钮获取中文摘要

Probing molecular structure of Pdx-P450cam binary complex by EPR and ENDOR spectroscopy : During the monooxygenation reaction by cytochrome P450cam, a complex of P450cam and reduced putidaredoxin (Pdx) is formed as an obligatory intermediate of the reaction. We found that EPR spectrum of the reduced Pdx in its binary complex with the camphor-bound ferrous P450cam was altered significantly upon ligation of OィイD22ィエD2, CO and NO to the ferrous heme of P450cam and that Arg-112 and 109 at the putative Pdx-binding site of P450cam played important roles associated with this phenomenon. X-band ィイD11ィエD1H-ENDOR results of the Pdx-P450cam binary complex demonstrated that the interactions of protons of cystein ligands with the unpaired electrons on the iron atoms in the reduced Pdx were altered upon CO binding to the ferrous heme of P450cam. We also found that the EPR spectrum of the reduced adrenodoxin (Adx) in its binary complex with cytochrome P450scc was altered upon CO binding to the ferrous heme of P450scc in the presence of 20S-hydroxy cholesterol, substrate analogue. Precise analyses are in progress.Crystallization of Pdx-P450cam binary complex : A substrate-free P450cam was crystallized having different crystalline form from that had been reported previously. Single crystal microspectrophotometry indicated that substrate-camphor never bound to P450cam in this crystal. X-ray crystallographic analysis of this substrate-free P450cam indicated that the positions of the side chains of the amino acid residues near the substrate-binding site were significantly altered as compared with the previously reported molecular structure. We have also made every effort to crystallize the binary complex of Pdx-P450cam. The crystallization of this binary complex is not succeeded until now. The efforts of the crystallization are in progress.