Abstract

A variant cytochrome P450 11β-hydroxylase/aldosterone synthase cDNA (CYP11B2) clone, pALDO-4, was isolated and sequenced from a rat zona glomerulosa cDNA library. This clone contains a 1521 bp open reading frame coding for a 506 amino acid residue protein which has a 30 amino acid extension peptide which is 6 residues longer than that reported by others. Seven nucleotide mutations in the coding region of the mature protein were found in comparison to the reported cDNAs. These mutations resulted in three amino acid changes in the mature protein which were identical to those present in the cytochrome P450 11β-hydroxylase (CYP11B1). Two nucleotide substitutions and two nucleotide insertions were also identified in the 3‧-noncoding region. The expression product of this cDNA transfected into COS7 cells converted DOC to aldosterone, corticosterone and 18-hydroxycorticosterone less efficiently than the plasmid containing the cDNA with normal 24 amino acid extension peptide.