 The protein encoded by its cDNA is composed of 508 amino acid residues.As an enzyme, CYP17A1 possesses an active site that associates with a heme prosthetic group to catalyze biosynthetic reactions.Based on its known structures while bound to two steroidal inhibitors, abiraterone and galeterone, CYP17A1 possesses the canonical cytochrome P450 fold present in other complex P450 enzymes that participate in steroidogenesis or cholesterol metabolism, though it orients the steroid ligands toward the F and G helices, perpendicular to the heme group, rather than the β1 sheet.