CYP21 mutations in simple virilizing congenital adrenal hyperplasia

We studied the functional and structural effects of two unique missense mut ations in CYP21 found in patients with simple virilizing congenital adrenal hy, perplasia. The rare variants L300F and V281G were found in two girls w ho were each hemizygous for one of the mutations. Functional analysis after expression in COS-1 cells revealed that the mutant enzymes had reduced enz ymatic activity for conversion of both 17-hydroxyprogesterone (L30OF 9.5%, V281G 3.9% of normal) and progesterone (L30OF 4.4%, V281G 3.9% of normal). Both mutant enzymes had an increased degradation in mammalian COS-1 cells c ompared to the normal protein, although the L30OF variant affected the degr adation pattern to a greater extent. Our data indicate that the residue L30 0 is important in maintaining normal structure of the 21-hydroxylase enzyme whereas mutations affecting V281 most likely cause impaired enzyme activit y by interfering with a specific function(s) of the protein.