Coding nucleotide sequence of rat NADPH-cytochrome P-450 oxidoreductase cDNA and identification of flavin-binding domains.

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Abstract
The coding nucleotide sequence of the mRNA for NADPH-cytochrome P-450 oxidoreductase (NADPH:ferricytochrome oxidoreductase, EC 1.6.2.4) from rat liver was determined from 2 overlapping c[complementary] DNA clones, pOR-7 and pOR-8, which together contain 2401 nucleotides complementary to rat liver oxidoreductase mRNA. The single open reading frame of 2034 nucleotides spanning these cDNA codes for a 678 amino acid polypeptide with a MW of 76,962. The deduced amino acid composition is in excellent agreement with that determined by direct amino acid analysis of purified rat liver P-450 oxidoreductase, and the amino-terminal region (residues 1-80) largely coincides with the amino-terminal sequence of the oxidoreductase isolated from rabbit liver. Comparison of the amino acid sequence to those of other flavoproteins revealed 2 separate domains that are likely to be involved in flavin binding: a long segment (residues 77-228) homologous with Desulfovibrio vulgaris flavodoxin, an FMN-containing protein, and a shorter segment (residues 452-477) homologous with the FAD-binding segment of fumarate reductase from Escherichia coli.