Fig. 1Schematic representation of the constructs used to measure P450c17 enzyme activity produced in human embryonic kidney cells 293T (HEK293T) cells. The entire coding regions of c.1118A>T, c.1148delA, and wild type (WT) cytochrome P450 17A1 (CYP17A1) complementary DNAs (cDNAs) were subcloned into the HindIII and KpnI site of pcDNA3 vector with a C-terminal flag tag. The positions of restriction enzymes, start (ATG) and stop (tga) codons, and HindIII, KpnI, and XhoI sites, are shown. Exons are indicated with arabic numerals and the mutation sites (c.1118A>T and c.1148delA) are indicated. The 1 bp deletion (bp position 1148 in c.1148delA, indicated by the arrow) results in a shift of the reading frame and a termination codon after 36 amino acids. pCMV, promoter cytomegalovirus; SV40, simian virus 40; MT1, mutant type 1; MT2, mutant type 2.
Fig. 2The compound cytochrome P450 17A1 (CYP17A1) heterozygote. (A) Pedigree of 17α-hydroxylase/17,20-lyase deficient family. Individuals are represented as follows: male (square); females (circles). The black symbol represents the c.1148delA allele and the gray symbol represents the c.1118A>T allele. The arrow indicates the compound heterozygous proband. The proband inherited mutations c.1118A>T and c.1148delT from her mother and father, respectively. (B) Subcloning of the compound heterozygous CYP17A1 gene. Polymerase chain reaction products of RNA from the proband's leucocytes were subcloned and sequenced to confirm heterozygous mutations. The c.1148delA mutation was found to be in exon 7 and the c.1118A>T mutation in exon 6. WT, wild type; A/T, A and T.
Fig. 3Expression and enzyme activities of P450c17 protein produced by cytochrome P450 17A1 (CYP17A1) complementary DNA (cDNA) overexpressed in human embryonic kidney cells 293T (HEK293T) cells. (A, B) Analysis of P450c17 proteins by Western blotting (WB) and immunofluorescence, respectively. Expression of c.1118A>T and the doubly transfected clone (p.H373L and p.E383fsX36) in HEK293T cells is significantly lower than that of wild type (WT) and no expression of c.1148delA mutant is detected. (C) Enzyme activity. Production of 17α-hydroxyprogesterone (17-OHP) in the presence of various concentrations of progesterone (P) (0, 1.0, and 2.0 µM) and production of dehydroepiandrosterone (DHEA) in the presence of various concentration of 17α-hydroxypregnenolone (17-PREG) (0, 1.0, and 2.0 µM). HEK293T cells were transfected with WT, c.1118A>T, c.1148delA, and co-transfection. Compared to the enzymatic activity against WT (744 nmol/L), the 17α-hydroxylase activity for the p.His373Leu mutant was reduced to 21.9 nmol/L and the 17,20-lyase activity for the p.Glu383fsX36 mutant was almost zero (1.3 nmol/L). Data are mean values of P450c17 activity assayed in triplicate. Data are expressed as mean±SD (n=3). DAPI, 4',6-diamidino-2-phenylindole.
Fig. 4Computer model of cytochrome P450 17A1 (CYP17A1) (PDB ID; 3SWZ). A, a ribbon diagram of the protein backbone, with heme (red) and highlighting p.His373, p.Glu383, p.His373Leu, p.Glu383Gly. Also shown are residues p.His373 and p.His373Leu in green and p.Glu383 and p.Glu383Gly in yellow. Substitution of His by Leu at amino acid position 373 results in loss of catalytic activity. Mutation of the His-deficient mutant at position 373 or substitution of Glu with Gly at position 383 prevents the incorporation of a heme group, rendering the mutant enzyme inactive. The imidazole side chain of His is a common ligand for the metal protein and is part of the catalytic site of the enzyme. His can participate in acidic catalysis by proton and non-proton states, but Leu does not bind to heme because there is no imidazole branch. Images were created in Swiss PDB viewer (Swiss Institute of Bioinformatics) and UCSF Chimera version 1.11.2 (University of California).
Table 1Comparison of p.His373 Mutations of CYP17A1 Gene Reported in the Literature
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Literature |
Study case |
[8] |
[27] |
[28] |
[29] |
[30] |
[31] |
Age, yr |
21 |
23 |
3.5 |
14 |
23 |
6 |
Ethnic |
Korean |
Korean |
Japanese |
Caucasian |
Chinese |
Japanese |
p.His373 mutation |
p.His373Leu |
p.His373Leu |
p.His373Asn |
p.His373Asp |
p.His373Leu |
p.His373Leu |
Opposite allele mutation |
p.Glu383fs |
p.His373Leu |
p.Phe53del |
p.Arg96Trp |
p.Asp487_Phe489del |
p.Leu247del |
Karyotype |
46,XX |
46,XX |
46,XY |
46,XX |
46,XX |
46,XY |
Sexual infantalism |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Hypertension |
No |
Yes |
No |
Yes |
Yes |
Yes |
Hypokalemia |
No |
No |
No |
Yes |
Yes |
Yes |