title: Rat testosterone 7 alpha-hydroxylase. Isolation, sequence, and expression of cDNA and its developmental regulation and induction by 3-methylcholanthrene.
abstract: A P-450, designated P-450a, with high testosterone 7 alpha-hydroxylase activity was purified from rat liver microsomes. Specific polyclonal antibody against this P-450 was used to screen a lambda gt11 expression cDNA library and a 1687-base pair cDNA was isolated and sequenced. The deduced protein had 492 amino acids, a calculated Mr of 56,016, and it shared 51 and 45% amino acid similarities to P-450e and P-450f, respectively. Regions of similarity were distributed in distinct areas of high and low similarity along the P-450a primary sequence. P-450a cDNA was introduced into yeast cells using the expression vector pAAH5, and the resultant yeast microsomes contained both a protein of identical electrophoretic mobility to that of rat P-450a and testosterone 7 alpha-hydroxylase activity. These results confirm enzyme reconstitution data and antibody inhibition data that P-450a possesses testosterone 7 alpha-hydroxylase activity. The antibody and cDNA probes were used to examine the mechanism of regulation of P-450a by inducers and during development. P-450a and its mRNA were present at low level in newborn rats and increased to maximal level at 1 week of age in both males and females. At age 12 weeks, however, the P-450a level decreased in males but remained elevated in females. Concomitant with the decrease in P-450a in adult males was an increase in level of another immunologically related P-450. In adult male rats, P-450a was induced almost 5-fold by administration of 3-methylcholanthrene and this induction was the result of an increase in its mRNA. These results establish testosterone 7 alpha-hydroxylase as a member of the P-450e gene family that is developmentally regulated, sex-dependent, and markedly inducible by 3-methylcholanthrene.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004247:DNA / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D007527:Isoenzymes / Q000096:biosynthesis; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D007527:Isoenzymes; D008748:Methylcholanthrene; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C022724:testosterone 7-alpha-hydroxylase, hamster