The topology of the mitochondrial 11β-hydroxylase system in bovine adrenal cortex

Binding of deoxycorticosterone to cytochrome P-450 of the 11β-hydroxylase system in adrenal cortex mitochondria was inhibited by the nonpenetrating protein reagent diazobenzenesulfonate in damaged but not in intact mitochondria. The slowly penetrating hydrophilic substrate deoxycorticosterone 21-sulfate showed a slow binding to cytochrome P-450 as compared to the hydrophobic nonesterified steroid. In contrast, the esterified and nonesterified steroids bound equally fast in sonicated, aged or lysolecithin-treated mitochondria. These data imply that the steroid substrates must penetrate the inner mitochondrial membrane to interact with the 11β-hydroxylase system.