A cDNA clone encoding δ4-3-ketosteroid 5β-reductase was isolated from rat liver cDNA libraries using antibodies specific for the enzyme and oligonucleotides as probes. The cDNA contained 981-base pair open reading frame encoding 327 amino acid residues (M, 37 376) and an unusually long 3′-untranslated region rich in AT sequence in the total length of 3189 base pairs. The predicted amino acid sequence contains th sequences similar to the putative NADPH- and steroid-binding regions.
