Human cytochrome P-450 4 mRNA and gene: Part of a multigene family that contains Alu sequences in its mRNA

Abstract

Several overlapping λgt11 cDNA clones have been sequenced and shown to encode for the full-length human cytochrome P-450 4. The structure and location of the exons and flanking intron regions were also identified from a λEMBL-3 human genomic clone that encodes the full-length human P-450 4 gene. The human P-450 4 mRNA is flanked by 62 base pairs of 5'- and 1508 base pairs of 3'-noncoding sequence, with 1548 bases that encode a protein of 516 amino acids (M(r), 58,376). The predicted amino acid sequence of human P-450 4 is 69% and 70% homologous to its equivalent in mouse and rat, respectively, 75% homologous to rabbit P-450 4, and 68% homologous to human P1-450. The 7.6-kilobase gene encodes 3118 nucleotides of exon sequence that is separated by six introns into seven exons. Exon 7, which is 1802 nucleotides, contains three inverse/complement Alu sequences that are organized in tandem. Comparison of the genomic DNA sequence of the human P-450 4 gene with the human P1-450 and related genes in rat and mouse and the identification of the amino acid residues and triplet codon at each exon-intron junction show that the location of each intron in the human P-450 4 gene is conserved within this gene family. Although the length and homology of the introns within a related gene family may not be conserved, the location of intronic sequences may be an important determinant in the identification of related P-450 genes.