Rat liver NAD(P)H:quinone reductase: isolation of a quinone reductase structural gene and prediction of the NH2 terminal sequence of the protein by double-stranded sequencing of exons 1 and 2.

Recently two reports [J. A. Robertson et al. (1986) J. Biol. Chem. 261, 15794-15799 and R. M. Bayney et al. (1987) J. Biol. Chem. 262, 572-575] have appeared concerning the nucleotide sequence of quinone reductase cDNA clones. Although the cDNA clones are virtually identical, they diverge in the 5' region that encodes the NH2 terminus of the protein. In order to clarify the sequence of this region, we have isolated quinone reductase clones from a rat genomic library using a cDNA clone, pDTD55, isolated and characterized by our laboratory. We have determined the sequence of exons 1 and 2 of the structural gene by double-stranded sequencing using oligonucleotide primers. The sequence of exons 1 and 2 of the quinone reductase structural gene along with our previous nucleotide sequence analysis of pDTD55 as well as conventional amino acid sequence analysis of the purified protein indicates that quinone reductase is composed of 274 amino acids with a molecular weight of 30,946. These data agree with the published sequence of lambda NMOR1 reported by Robertson et al.