A full-length cDNA clone. (1,894 nucleotides) of mouse cytochrome P3-450 was isolated with the Okayama-Berg vector and sequenced.
An open reading frame spanned positions 61 to 1602. The first 25, and three of the last five, amino acids of P3-450 are identical
to those found in the amino- and carboxy-terminus, respectively, of the rat P-450d protein. Mouse P3-450 protein has 513 residues,
and a
... [Show full abstract] molecular weight of 58,223 with six cysteine residues. P3-45O nucleotides 305 to 352 exhibit 74% homology, and nucleotides
1068 to 1260, 69% homology, with portions of rat P-450b exons 2 and 7, respectively. P3-450 shows 62% homology in the so-called
“highly conserved region” of 39 nucleotides in the rat P-450b and P-450e and the mouse P-450b. These results indicate that
P3-450, P-450b and P-450e arose from a common ancestral gene. Cysteinyl peptide-coding regions were examined: P3-450 nucleotides
1405 to 1464 exhibit 61% homology, and nucleotides 502 to 552 exhibit 37% homology, when compared with their corresponding
regions in the rat P-450b gene. These data support the likelihood that cysteine 456 is the thiolate ligand to the heme iron
in the P3-45O enzyme active-site.