[Effect of chemical modification of tyrosine residues of cholesterol-hydroxylating cytochrome P-450 on the interaction with high-spin effectors].

The role of tyrosine residues of cytochrome P-450scc in the interaction with adrenodoxin and cholesterol was investigated, using chemical modifications with tetranitromethane. Selective chemical modification of tyrosine residues resulted in hemoprotein inactivation. Nitration changed the kinetic parameters of the cholesterol side chain cleavage reaction. Both high spin effectors, i.e., substrate and adrenodoxin, prevent cytochrome P-450scc from the inactivation caused by tetranitromethane. Modification of cytochrome P-450scc decreased the affinity of the hemoprotein for cholesterol and adrenodoxin. Some direct evidence for tyrosine involvement in the interaction between cytochrome P-450scc and adrenodoxin was obtained through the use of zonal affinity chromatography on immobilized ferredoxin.