Evidence for the functional role of residues in the B'-C loop of baboon cytochrome P450 side-chain cleavage (CYP11A1) obtained by site-directed mutagenesis, kinetic analysis and homology modelling

Cytochrome P450 side-chain cleavage: insights gained from homology modeling

Cytochrome P450 side-chain cleavage (CYP11A1) catalyzes the conversion of cholesterol to pregnenolone, the first step in steroidogenesis. The absence of a solved crystal structure has complicated deductions pertaining to the structure/function relationships of this key enzyme. Although a number of techniques have been employed to identify domains and specific amino acid residues important for catalytic activity, these methods have been unsuccessful in predicting three-dimensional orientations in space and thus the mechanism by which they exert their kinetic effect. This review aims to demonstrate the significant contribution homology modelling, when employed as a tool in combination with other standard biochemical techniques, has made towards our understanding of CYP11A1.