Endogenous cysteine ligation in ferric and ferrous cytochrome P-450. Direct evidence from x-ray absorption spectroscopy.

摘要: Extended x-ray absorption fine structure spectroscopy has been applied to the elucidation of heme iron site bacterial cytochrome P-450. The low spin ferric, high ferrous, and ferrous carbonyl states enzyme have examined. Curve-fitting analysis data provides direct compelling evidence for presence a sulfur atom in first coordination sphere iron. iron-nitrogen (porphyrin) distances indicate five ferric P-450 six iron-sulfur are consistent with thiolate ligation, presumably from cysteinate, all four enzyme. In each case, bond distance is equal or shorter than analogous Fe-S bonds model porphyrin complexes whose crystal structures determined. Since known thiol-sulfur:iron-heme noticeably longer corresponding bonds, X-ray results strongly suggest that, state examined, donor thiolate. reported this paper concerning ligand identity, protonation, metal-ligand critical importance complete description reaction cycle its mechanism oxygen activation.