Complete amino acid sequence of 21-hydroxylase cytochrome P-450 from porcine adrenal microsomes

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency

More than 90% of cases of congenital adrenal hyperplasia (CAH, the inherited inability to synthesize cortisol) are caused by 21-hydroxylase deficiency. Females with severe, classic 21-hydroxylase deficiency are exposed to excess androgens prenatally and are born with virilized external genitalia. Most patients cannot synthesize sufficient aldosterone to maintain sodium balance and may develop potentially fatal "salt wasting" crises if not treated. The disease is caused by mutations in the CYP21 gene encoding the steroid 21-hydroxylase enzyme. More than 90% of these mutations result from intergenic recombinations between CYP21 and the closely linked CYP21P pseudogene. Approximately 20% are gene deletions due to unequal crossing over during meiosis, whereas the remainder are gene conversions--transfers to CYP21 of deleterious mutations normally present in CYP21P. The degree to which each mutation compromises enzymatic activity is strongly correlated with the clinical severity of the disease in patients carrying it. Prenatal diagnosis by direct mutation detection permits prenatal treatment of affected females to minimize genital virilization. Neonatal screening by hormonal methods identifies affected children before salt wasting crises develop, reducing mortality from this condition. Glucocorticoid and mineralocorticoid replacement are the mainstays of treatment, but more rational dosing and additional therapies are being developed.

The P450 superfamily: update on new sequences, gene mapping, accession numbers, early trivial names of enzymes, and nomenclature

We provide here a list of 221 P450 genes and 12 putative pseudogenes that have been characterized as of December 14, 1992. These genes have been described in 31 eukaryotes (including 11 mammalian and 3 plant species) and 11 prokaryotes. Of 36 gene families so far described, 12 families exist in all mammals examined to date. These 12 families comprise 22 mammalian subfamilies, of which 17 and 15 have been mapped in the human and mouse genome, respectively. To date, each subfamily appears to represent a cluster of tightly linked genes. This revision supersedes the previous updates [Nebert et al., DNA 6, 1-11, 1987; Nebert et al., DNA 8, 1-13, 1989; Nebert et al., DNA Cell Biol. 10, 1-14 (1991)] in which a nomenclature system, based on divergent evolution of the superfamily, has been described. For the gene and cDNA, we recommend that the italicized root symbol "CYP" for human ("Cyp" for mouse), representing "cytochrome P450," be followed by an Arabic number denoting the family, a letter designating the subfamily (when two or more exist), and an Arabic numeral representing the individual gene within the subfamily. A hyphen should precede the final number in mouse genes. "P" ("p" in mouse) after the gene number denotes a pseudogene. If a gene is the sole member of a family, the subfamily letter and gene number need not be included. We suggest that the human nomenclature system be used for all species other than mouse. The mRNA and enzyme in all species (including mouse) should include all capital letters, without italics or hyphens. This nomenclature system is identical to that proposed in our 1991 update. Also included in this update is a listing of available data base accession numbers for P450 DNA and protein sequences. We also discuss the likelihood that this ancient gene superfamily has existed for more than 3.5 billion years, and that the rate of P450 gene evolution appears to be quite nonlinear. Finally, we describe P450 genes that have been detected by expressed sequence tags (ESTs), as well as the relationship between the P450 and the nitric oxide synthase gene superfamilies, as a likely example of convergent evolution.

Sequences of the swine 21-hydroxylase gene (CYP21) and a portion of the opposite-strand overlapping gene of unknown function previously described in human

We sequenced a 4.8 kb BamHI swine genomic fragment comprising the entire 21-hydroxylase gene (CYP21) and its 5' and 3' flanking segments. The CYP21 coding sequence spanned 3050 bp and as in other species, comprised 10 exons separated by the corresponding introns. The deduced protein corresponded to 492 amino acid residues, 8 of which differed from a previously sequenced swine CYP21 enzyme. The 5' flanking region displayed several putative cis-acting elements which may be involved in either constitutive or cyclic adenosine 3',5'-monophosphate (cAMP) dependent transcriptional expression. We also characterized within the 5' region a 139 bp repetitive element of the short interspersed nucleotide element (SINE) family located on the opposite strand. In addition, we characterized the last five exons of a human-like opposite strand gene (OSG/X) located in the swine at the 3' end of CYP21. The sequenced part of this OSG/X displayed a very strong homology with its human counterpart.

Steroid 21-hydroxylase deficiency: three additional mutated alleles and establishment of phenotype-genotype relationships of common mutations

Lesions in the gene encoding steroid 21-hydroxylase [steroid hydrogen-donor: oxygen oxidoreductase (21-hydroxylating), EC 1.14.99.10] result in defective adrenal steroid synthesis; the severe forms are known as congenital adrenal hyperplasia. To facilitate complete characterization of mutations in this region of tandemly repeated genes, we have developed selective PCR amplification and direct sequencing of full-length nonpseudogene steroid 21-hydroxylase genes. This technique identifies known mutations, characterizes or excludes unknown mutations, and determines the gene-copy number. Three additional defective alleles were found. A Gly-292----Ser mutation and a frameshift mutation at Arg-484 (GG----C) were identified in patients with severe steroid 21-hydroxylase deficiency. An allele with three additional sequence variations--C----T at 4 bases upstream of translation initiation, Pro-106----Leu, and Pro-454----Ser--were identified in two siblings with late-onset deficiency. Pro-454 is conserved in four species, indicating its importance for normal enzyme function. Functional consequences of individual alleles have been determined in vivo by studying individuals with only one steroid 21-hydroxylase gene. Detailed analyses of clinical data revealed that genotyping could predict the clinical course of the disease. The locations of disease-causing mutations on different haplotypes of the steroid 21-hydroxylase gene region are described.

The swine steroid 21-hydroxylase gene (CYP21): cloning and mapping within the swine leucocyte antigen complex

A swine genomic cosmid library constructed from a genotypically SLA homozygous Large White individual was screened with a murine genomic 21-hydroxylase probe. A clone which contained a pig 21-hydroxylase gene was isolated and after subcloning, the 5' region of the gene was sequenced. The deduced amino acid sequence corresponded almost exactly to the NH2 terminal portion of the steroid 21-hydroxylase from porcine adrenal microsomes. Comparison of the first 99 amino acid residues of both sequences revealed three substitutions comprising two leucine residues in positions 10 and 13, and one arginine residue in position 55 for our sequence, instead of threonine in position 10 and lysine in position 13 and 55 for the isolated enzyme. A swine homologous probe was derived from the isolated 21-hydroxylase gene and used for gene assignment by RFLP studies in two swine leucocyte antigen (SLA) informative families. The results demonstrate that the swine 21-hydroxylase gene is located within or close to the swine MHC. Taken together, the present results suggest the existence of a single 21-hydroxylase gene per haploid genome.

Molecular cloning and sequence analysis of cDNA encoding rat adrenal cytochrome P-450(11)beta

A cDNA clone encoding cytochrome P-450(11)beta of rat adrenal has been cloned and sequenced using a bovine P-450(11)beta cDNA insert (pcP-450(11 beta)-2; (1987) J. Biochem. 102, 559-568) as a probe. The nucleotide sequence contains an open reading frame sufficient to encode the entire amino acid sequence of a P-450(11)beta precursor protein consisting of 499 amino acids including an extension peptide of 24 amino acids at the NH2-terminus. The cDNA contains 1247 nucleotides at the 3'-noncoding region including 51 nucleotides of poly A, but lacks the 5'-noncoding region. The deduced amino acid sequence shows 61% similarity to that of bovine P-450(11)beta. Putative binding sites for heme and steroid are highly conserved among steroidogenic P-450s of known structure.

Clinical and genetic characterization of nonclassic 21-hydroxylase deficiency

Nonclassic steroid 21-hydroxylase deficiency is a frequent, relatively mild disorder of cortisol biosynthesis characterized by variable signs of postnatal androgen excess. It is inherited as an allelic variant of the CYP21B gene encoding the 21-hydroxylase enzyme. CYP21B is located in the HLA histocompatibility complex, and a nonclassic allele is often associated with characteristic HLA antigens: B14;DR1. A CYP21B gene from a HLA-B14;DR1 homozygous patient with nonclassic 21-hydroxylase deficiency was cloned and analyzed. Five deviations from the normal sequence of CYP21B were found, but only one appeared likely to affect the functional integrity of the protein: codon 281, GTG, encoding valine, was changed to TTG, leucine. An oligonucleotide probe was constructed corresponding to the mutant sequence surrounding codon 281 and hybridized with DNA samples digested with restriction endonuclease Taq I. Samples from 8 nonclassic 21-hydroxylase deficiency patients carrying HLA-B14;DR1 contained a hybridizing fragment 3700 base-pairs long, indicating presence of the val-281 mutation in the CYP21B gene. In contrast, unaffected individuals and one patient who lacked HLA-B14;DR1 showed no evidence of the val-281 mutation in CYP21B. We conclude that the codon 281 mutation is a consistent molecular genetic marker for nonclassic 21-hydroxylase deficiency associated with HLA-B14;DR1.

The P450 superfamily: updated listing of all genes and recommended nomenclature for the chromosomal loci

In this update we provide a list of the 71 P450 genes and the four P450 pseudogenes that have been characterized as of September 30, 1988. The chromosomal locations of many of these genes are also summarized. A modest revision of the initially proposed nomenclature of the P450 superfamily (Nebert et al., DNA 6, 1-11, 1987) is described specifically for the human and mouse chromosomal loci. The motivation for this revision is to conform to the rules of nomenclature for human and mouse genes. Recommendations for the naming of chromosomal loci include the root symbol "CYP" for human ("Cyp" for mouse), denoting "cytochrome P450." We recommend that this root also be used for other organisms. For a chromosomal locus, the root symbol is followed by an Arabic numeral designating the P450 family, a letter indicating the subfamily, and an Arabic numeral representing the individual gene within the family or subfamily. Numbers of the individual genes usually will be assigned in the order the genes are identified. This system is consistent with our earlier proposed nomenclature for P450 families and gene products from all eukaryotes and prokaryotes.

Molecular genetic analysis of nonclassic steroid 21-hydroxylase deficiency associated with HLA-B14,DR1

Nonclassic steroid 21-hydroxylase deficiency is a frequent, relatively mild disorder of cortisol biosynthesis, characterized by variable signs of postnatal androgen excess. It is inherited as an allelic variant of the gene designated CYP21B, which encodes 21-hydroxylase. CYP21B is located in the HLA histocompatibility complex, and a "nonclassic" allelic variant is often associated with characteristic HLA antigens--B14,DR1. We cloned and analyzed the CYP21B gene from a patient homozygous for HLA-B14,DR1 who had nonclassic 21-hydroxylase deficiency. Five deviations from the normal genetic sequence of CYP21B were found, but only one appeared likely to affect the functional integrity of the protein: codon 281, GTG, encoding valine, was changed to TTG, leucine. We constructed an oligonucleotide probe corresponding to the mutant DNA sequence surrounding codon 281 and hybridized the probe with DNA samples digested with the restriction endonuclease Taql. Samples from eight patients with nonclassic 21-hydroxylase deficiency who had the haplotype HLA-B14,DR1 contained a hybridizing fragment 3700 base pairs long, indicating the presence of the valine-281 mutation in the CYP21B gene. In contrast, unaffected subjects and one patient with nonclassic deficiency who did not have HLA-B14,DR1 had no evidence of this mutation. We conclude that the mutation in codon 281 is a consistent molecular genetic marker for nonclassic 21-hydroxylase deficiency associated with HLA-B14,DR1.