title: cDNA and derived amino acid sequence of ethanol-inducible rabbit liver cytochrome P-450 isozyme 3a (P-450ALC).
abstract: Administration of ethanol to rabbits is known to induce a unique liver microsomal cytochrome P-450, termed isozyme 3a or P-450ALC, which is responsible for the increased oxidation of ethanol and other alcohols and the activation of toxic or carcinogenic compounds such as acetaminophen and N-nitrosodimethylamine. To further characterize this cytochrome P-450 we have identified cDNA clones to isozyme 3a by immunoscreening, DNA hybridization, and hybridization-selection. The cDNA sequence determined from two overlapping clones contains an open reading frame of 1416 nucleotides, and the first 25 amino acids of this reading frame correspond to residues 21-45 of cytochrome P-450 3a. The complete polypeptide, including residues 1 to 20, contains 492 amino acids and has a molecular weight of 56,820. Cytochrome P-450 3a is approximately 55% identical in sequence to P-450 isozymes 1 and 3b and 48% identical to isozyme 2. Hybridization of clone p3a-2 to electrophoretically fractionated rabbit liver poly(A)+ RNA revealed multiple bands, but, with a probe derived from the 3' nontranslated portion of this cDNA, only a 1.9-kilobase band was observed. Treatment of rabbits with imidazole, which increases the content of isozyme 3a, resulted in a transient increase in form 3a mRNA, but this was judged to be insufficient to account for the known 4.5-fold increase in form 3a protein. Genomic DNA analysis indicated that the cytochrome P-450 3a gene does not belong to a large subfamily.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000032:analysis*; D004262:DNA Restriction Enzymes; D004790:Enzyme Induction; D000431:Ethanol / Q000494:pharmacology*; D005796:Genes; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics*; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D011817:Rabbits
chemical_list: D007527:Isoenzymes; D000431:Ethanol; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D004262:DNA Restriction Enzymes