Molecular cloning and expression in Saccharomyces cerevisiae of tobacco NADPH-cytochrome P450 oxidoreductase cDNA.

We obtained information on the full length tobacco NADPH-cytochrome P450 oxidoreductase (P450 reductase) by a combination of the cDNA clone pCTR1 and the genomic DNA clone pGTR1. The deduced primary structure consisting of 713 amino acid residues contained sequences corresponding to FMN, FAD, and NADPH-binding regions. Based on this information, we prepared the full-length cDNA pFTR of tobacco P450 reductase by RT-PCR and expressed it in the yeast Saccharomyces cerevisiae. The transformed yeast cells carrying pFTR produced the corresponding mRNA and protein, and had increased cytochrome c reductase activity in the microsomes. An in vitro reconstitution system of the yeast microsomal fractions expressed tobacco P450 reductase and rat P450 1A1 showed an increased 7-ethoxycoumarin O-deethylase activity. These results indicated that tobacco P450 reductase expressed in the yeast microsomes coupled with rat P450 1A1 resulting in an increased monooxygenase activity.