Immunochemical characterization of steroid hydroxylases of adrenocortical mitochondria. 1. Antibodies as inhibitors of cytochrome P450scc (CYP11A1) and P450(11 beta) (CYP11B1) activities.

The effects of antibodies against protein components of the monooxygenase systems of adrenocortical mitochondria on the reactions of hydroxylation of cholesterol and 11 beta-deoxycorticosterone were investigated in a reconstituted system containing cytochromes P450scc (CYP11A1) and P450(11 beta) (CYP11B1) as the terminal oxidases and the electron-transfer proteins adrenodoxin reductase and adrenodoxin. It has been shown that affinity-purified antibodies to cytochromes P450scc and P450(11) beta are efficient modulators of the activity of these systems, and their inhibiting effect is mainly due to interference with the interaction of heme proteins and adrenodoxin. The antibodies against polypeptide fragments of the cytochrome P450scc molecule F1 (Ile1-Arg256), F2 (Asn257-Ala481), and F3 (Asn257-Arg399) were used to demonstrate that the interaction of heme protein with adrenodoxin has a multisite character and involves regions located in the N- and C-terminal sequences of cytochrome P450scc.