The structure and activity of two cytochrome P450 sub(c21) proteins encoded in the ovine adrenal cortex

The steroidogenic enzyme cytochrome P450 sub(c21) (CYP21A1) is synthesized in the adrenal cortex and is essential for cortisol and aldosterone production. We have studied the structure and activity of ovine P450 sub(c21) proteins by analysis and expression of the corresponding cDNAs. Two P450 sub(c21) mRNAs (2.2 and 1.7 kilobases) were detected in ovine adrenal RNA and corresponded to two types of P450 sub(c21) cDNA clones that differed in their 3' region. One clone encoded a protein similar in structure to bovine, murine, and human P450 sub(c21) proteins. The other clone contained a 3' deletion of about 500 nucleotides and encoded a P450 sub(c21) protein that was truncated by 18 residues at the carboxyl terminus. The boundaries of this deletion suggested that an additional splicing event was responsible for the shortened mRNA sequence.