Molecular cloning of cDNA for cholesterol 7 alpha-hydroxylase from rat liver microsomes. Nucleotide sequence and expression.

A complete cDNA clone encoding cholesterol 7 alpha-hydroxylase was isolated from a rat liver cDNA library by the use of specific antibodies to the enzyme. The isolated cDNA clone was 3.6 kbp long and contained a 1509-bp open reading frame encoding 503 amino acid residues (Mr = 56,880). The identity of the cDNA was confirmed by expression of cholesterol 7 alpha-hydroxylase activity and the immunoreactive protein in COS cells transfected with pSVL expression vector carrying the cDNA insert. The primary structure of cholesterol 7 alpha-hydroxylase deduced from the nucleotide sequence of the cDNA indicated that the enzyme constitutes a novel P-450 family.