title: Gene structure of human cytochrome P-450(SCC), cholesterol desmolase.
abstract: Four independent clones containing a part of the P-450(SCC), cholesterol desmolase, gene were isolated from human genomic libraries using bovine P-450(SCC) cDNA as a probe. These clones covered the entire P-450(SCC) gene except for a part of the 1st intron. The gene is at least 20 kb long and is split into 9 exons by 8 introns. The sequence analysis revealed that the nine separated exons code for a primary structure consisting of 521 amino acids which shows 72% homology with that of bovine P-450(SCC). A CATT sequence and a TATAAT sequence, which are possibly a "CAT" box, and a "TATA" box, respectively, are present 129 and 91 bp upstream from the initiation codon. An unusual exon/intron junctional sequence that begins with GC was found in the 6th intron of the gene. A putative extension peptide consisting of 39 amino acids was found in the sequence of human P-450(SCC) by comparison with that of the bovine counterpart. Two conserved regions were found in the extension peptide of these two forms of P-450(SCC), suggesting a functional role of the portions in the mitochondrial localization and processing of P-450(SCC) precursor. The mature form of human P-450(SCC) has only one cysteine residue, which was located in the center of the HR2 region (Gotoh et al. (1983) J. Biochem. 97, 807-817). This observation established beyond doubt that the sole cysteine residue in the HR2 region is the 5th ligand to the heme.
mesh_terms: D001483:Base Sequence; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004262:DNA Restriction Enzymes; D005091:Exons; D005796:Genes; D006801:Humans; D007438:Introns; D008928:Mitochondria / Q000502:physiology; D010088:Oxidoreductases / Q000235:genetics*
chemical_list: D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D004262:DNA Restriction Enzymes