Primary structures of multiple forms of cytochrome P-450 isozyme 2 derived from rabbit pulmonary and hepatic cDNAs

Rabbit pulmonary and hepatic mRNA was used to construct cDNA libraries that were screened with a cDNA probe (pf 3/46) to murine cytochrome P-450 homologous with rat cytochrome P-450b. Three types of cDNA clones were identified on the basis of restriction analysis with Bst EII. Two types of clones (B0 and B1) were present in a library constructed from pulmonary mRNA. The nucleotide sequence of B0 cDNA encodes a protein of 491 amino acids having a sequence identical to one reported for isozyme 2. The sequence derived from the b1 cDNA also contains 491 amino acids but differs from the B0 sequence at six positions. B1 clones were also obtained from a library constructed from hepatic mRNA isolated 12 hr after a single treatment with phenobarbital. A third type of clone (B2) was also obtained from this library, but no B0 clones were found. The sequence derived from the B2 cDNA contains 491 amino acids and differs from the B0 and B1 sequences at 11 and 15 positions, respectively. A second hepatic cDNA library, constructed from mRNA from the liver of a rabbit treated with phenobarbital daily for 4 days, contained B0 clones. The sequence of one of these was found to be identical to that of the pulmonary B0 clones.