Hybrid cytochromes P-450 identify a substrate binding domain in P-450IIC5 and P-450IIC4

摘要: The cytochrome P-450 superfamily of enzymes catalyzes the oxidative metabolism innumerable lipophilic compounds (e.g., drugs, carcinogens, steroids). Although three-dimensional structure a soluble bacterial (P-450cam) has been solved, little is known about structures membrane-bound mammalian P-450s. Thus, structural features these that determine their multisubstrate specificity are unknown. In this report, we identify segment primary structurally similar but functionally distinct cytochromes P-450IIC5 and P-450IIC4, which determines apparent affinity for conversion progesterone into mineralocorticoid deoxycorticosterone. exhibits greater than 10-fold lower Km P-450IIC4 21-hydroxylation. Chimeric cDNAs were constructed expressed in COS-1 cells, encode hybrids between enzymes. hybrid assayed catalytic activity compared to parental proteins. A was identified conferred P-450IIC4. Sequential reduction length exchanged segments led enzyme with high derived largely from contains three amino acid residues clustered positions 113 118. This suggests region part substrate binding domain. maps by alignment sequences residue P-450cam, implicated binding, suggesting serve functional role two distantly related