title: Effects of cholesterol and adrenodoxin binding on the heme moiety of cytochrome P-450scc: a resonance Raman study.
abstract: The effects of cholesterol and adrenodoxin binding on resonance Raman spectra of cytochrome P-450scc in both oxidized and CO-reduced states were examined. Upon cholesterol binding, oxidized cytochrome P-450scc showed a significant shift of spin equilibrium from low-spin to high-spin state. Addition of adrenodoxin caused a complete conversion of cholesterol-bound oxidized cytochrome P-450scc to a pure high-spin state that was considered to be in the hexacoordinated state judged by the v10 mode at 1620 cm-1 and v3 mode around 1485 cm-1. Cholesterol in substrate binding site may oppose a linear and perpendicular binding of carbon monoxide to the reduced heme iron, leading to the distorted Fe-C-O linkage. This is based on the following observations: (1) an increase of the Fe-CO stretching frequency to 483 from 477 cm-1 upon addition of cholesterol; (2) an enhanced photodissociability of bound carbon monoxide of CO complex of cytochrome P-450scc in the presence of cholesterol. As another aspect of the effect of cholesterol on the CO complex form of cytochrome P-450scc, the enhanced stability of the native form ("P-450" form) was observed. There was no additional effect of reduced adrenodoxin on the Raman spectra of the CO-reduced form of cytochrome P-450scc.
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism; D000325:Adrenodoxin / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism; D011485:Protein Binding; D013059:Spectrum Analysis, Raman / Q000379:methods
chemical_list: D000325:Adrenodoxin; D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol