Electron paramagnetic resonance study of ferrous cytochrome P-450/sub scc/-nitric oxide complexes: effects of cholesterol and its analogs

Journal Article · Tue Jul 14 00:00:00 EDT 1987 · Biochemistry; (United States)

OSTI ID:6070510

Tsubaki, M; Hiwatashi, A; Ichikawa, Y; Hori, H

Electron paramagnetic resonance (EPR) spectra of nitric oxide (NO) complexes of ferrous cytochrome P-450/sub scc/ were measured at 77 K for the first time without using the rapid-mixing and freeze-quenching technique. Without substrate the EPR spectra were very similar to those of cytochrome P-450/sub cam/ (from Pseudomonas putida) and cytochrome P-450/sub LM/ (from rat liver microsomes) with rhombic symmetry; g/sub x/ = 2.071, g/sub z/ = 2.001, g/sub y/ = 1.962, and A/sub z/ = 2.2 mT for /sup 14/NO complexes. Upon addition of substrates, the EPR spectra exhibited many variations having rhombic symmetry in the major component and an additional minor component with less rhombic symmetry. Furthermore, addition of 20(S)-hydroxycholesterol caused a striking change in the EPR spectrum. The component with rhombic symmetry disappeared completely, and the component with less rhombic symmetry dominated (g/sub x/ = 2.027, g/sub z/ = 2.007, g/sub y/ = 1.984, and A/sub z/ = 1.76 mT for /sup 14/NO complexes). These observations suggest the existence of the following physiologically important natures: (1) the conformational flexibility of the active site of the enzyme due to the steric interaction between the substrate and the heme-bound ligand molecule and (2) the importance of the hydroxylation of the cholesterol side chain at the 20S position to proceed the side-chain cleavage reaction in cytochrome P-450/sub scc/.

• Research Organization: Kagawa Medical School, Japan
• OSTI ID: 6070510
• Journal Information: Biochemistry; (United States), Vol. 26:14
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
CYTOCHROMES
ELECTRON SPIN RESONANCE
NITRIC OXIDE
CHOLESTEROL
COMPLEXES
IRON COMPLEXES
LABELLED COMPOUNDS
NITROGEN 14
TEMPERATURE DEPENDENCE
CHALCOGENIDES
HYDROXY COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NITROGEN COMPOUNDS
NITROGEN ISOTOPES
NITROGEN OXIDES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PIGMENTS
PROTEINS
RESONANCE
STABLE ISOTOPES
STEROIDS
STEROLS
TRANSITION ELEMENT COMPLEXES
550601* - Medicine- Unsealed Radionuclides in Diagnostics