We elucidated the molecular basis of 17α-hydroxylase deficiency in a Chinese patient with male pseudohermaphroditism. The patient is a compound heterozygote, carrying two different mutant alleles in the CYP17 gene. The first mutation, g.6333–6341delGACTCTTTCA, located in exon 8, was reported in a Thai patient living in a rural village in Thailand. We suggest that g.6333–6341delGACTCTTTCA may be a prevalent mutation causing P450c17 deficiency in Southeast Asia. The second mutation is a missense mutation, g.5582C>G, located in exon 7, changing the codon 409 from CCG to CGG, and changing the coded amino acid from proline to arginine, i.e., P409R. This proline residue is conserved in P450c17 of other species and other human P450 proteins. Site-directed mutagenesis, in vitro expression, and functional analysis of the P409R mutant in COS-1 cells show that it has a complete lack of 17α-hydroxylase activity. The proline residue probably causes a turn in the meander region of P450c17, and we hypothesize, by comparison to homologous proteins, that the change in the protein conformation may abolish heme incorporation or may prevent P450c17 from interacting with electron donors.
Department of Chemical Pathology 2:
Department of Pediatrics, University of California, San Francisco, California, 94143-0978 3:
Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China 4:
University College London Medical School, Middlesex Hospital, United Kingdom