Formation of a cytochrome P-450 scc-adrenodoxin complex

Abstract

A cytochrome P-450 (P-450scc), the substrate- and oxygen-binding component of bovine adrenal cortex mitochondrial cholesterol desmolase system forms a stable complex with adrenal ferredoxin (adrenodoxin). The complex formation is indicated either by a change of the absorption spectrum of P-450scc or, more directly, by gel filtration and density gradient centrifugation techiniques. The molar ratio of P-450scc and adrenodoxin is found to be 1:1 and the spectral dissociation constant for the binding, 160 nM. The binding can be induced only in the presence of bound cholesterol to P-450scc. Thermal inactivation experiments provide additional evidence that indicates P-450scc combines with adrenodoxin to form a complex having a more rigid structure than P-450scc.