title: Structural analysis of cloned cDNA for mRNA of microsomal cytochrome P-450(C21) which catalyzes steroid 21-hydroxylation in bovine adrenal cortex.
abstract: We have isolated cDNA clones of the mRNA for cytochrome P-450 that catalyzes the steroid C-21 hydroxylation (P-450(C21)), which specifically catalyzes 21-hydroxylation of steroids in the microsomes of bovine adrenal cortex by using synthetic oligonucleotides as probes. Sequence determination of the cloned cDNA showed that it contains 2157 nucleotides and a poly(A) chain and that a single open reading frame of 1488 nucleotides codes for a polypeptide of 496 amino acids with a molecular weight of 56,113. The deduced amino acid composition is in agreement with that determined by direct amino acid analysis of purified P-450(C21) and the predicted primary structure contained amino acid sequences of N-terminal region and two internal tryptic fragments of the protein so far analyzed. Comparing the amino acid sequence with those of other forms of P-450 reveals that a conserved amino acid sequence containing a putative heme-binding cysteine is present in the equivalent position, proximate to the COOH terminus of the molecules and that P-450(C21) is phylogenically situated in an intermediate position between steroidogenic mitochondrial cytochrome P-450 which catalyzes the side-chain cleavage of cholesterol (P-450(SCC)) and drug-metabolizing microsomal P-450s. However, the amino acid sequence of P-450(C21) is much closer to that of drug-metabolizing P-450s than to that of P-450(SCC).
mesh_terms: D000302:Adrenal Cortex / Q000201:enzymology*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004247:DNA / Q000032:analysis*; D004262:DNA Restriction Enzymes / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D012333:RNA, Messenger / Q000235:genetics*; D013255:Steroid 21-Hydroxylase / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013552:Swine
chemical_list: D000596:Amino Acids; D012333:RNA, Messenger; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase; D004262:DNA Restriction Enzymes