[Structure-activity characteristics of cytochrome P-450c21. Immunochemical approaches and limited proteolysis]

To elucidate the general principles of the structural organization and functioning among mitochondrial and microsomal steroidogenic cytochromes P-450, a comparative study of the molecular organization of microsomal cytochrome P-450c21 and mitochondrial cytochrome P-450scc from adrenal cortex has been performed using immunochemical approaches and limited proteolysis. An efficient method to isolate and purify cytochrome P-450c21 has developed and the antibodies against the hemoprotein raised and characterized. Limited trypsinolysis of cytochrome P-450c21 leads to the formation of two fragments tightly bound to the microsomal membrane. Proteolytic modification is accompanied by spectral changes and the decreases of the catalytic activity. Possible models of the molecular organization of cytochrome P-450c21 are discussed in comparison with mitochondrial cytochrome P-450scc and liver microsomal cytochrome P-450.