Inhibitory domain-specific antibodies to cytochrome P-450scc

Highly specific antibodies to cytochrome P-450scc and its F1 and F2 fragments, representing N- and C-terminal sequences of the hemeprotein respectively, were raised in rabbits. These antibodies were found to be inhibitory (up to 50-90%) for the cholesterol transformation into pregnenolone in the reconstituted system, indicating the involvement of both F1 and F2 domains formed by the respective fragments in monooxygenase catalysis. Cytochrome P-450scc in mitoplasts is not accessible for trypsin as revealed by immunological techniques. However, the treatment of submitochondrial particles with trypsin results in two main fragments identified by immunoblotting in the presence of the monospecific antibodies as F1 and F2 fragments. This indicates that the trypsin sensitive 250-257 region in cytochrome P-450scc molecule connecting both domains is exposed to the matrix side of the inner mitochondrial membrane.