title: Cytochrome c biogenesis in mitochondria--Systems III and V.
abstract: In c-type cytochromes, heme becomes covalently attached to the polypeptide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein. There are two such cytochromes in mitochondria: cytochrome c and cytochrome c(1). The heme attachment is a post-translational modification that is catalysed by different biogenesis proteins in different organisms. Three types of biogenesis system are found or predicted in mitochondria: System I (the cytochrome c maturation system); System III (termed holocytochrome c synthase (HCCS) or heme lyase); and System V. This review focuses primarily on cytochrome c maturation in mitochondria containing HCCS (System III). It describes what is known about the enzymology and substrate specificity of HCCS; the role of HCCS in human disease; import of HCCS into mitochondria; import of apocytochromes c and c(1) into mitochondria and the close relationships with HCCS-dependent heme attachment; and the role of the fungal cytochrome c biogenesis accessory protein Cyc2. System V is also discussed; this is the postulated mitochondrial cytochrome c biogenesis system of trypanosomes and related organisms. No cytochrome c biogenesis proteins have been identified in the genomes of these organisms whose c-type cytochromes also have a unique mode of heme attachment.
authors: Department of Biochemistry, University of Oxford, Oxford, UK. james.allen@bioch.ox.ac.uk
authors: James W A
authors: JW
authors: Allen
mesh_terms: D000818:Animals; D045304:Cytochromes c / Q000378:metabolism*; D006801:Humans; D008190:Lyases / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D045304:Cytochromes c; D008190:Lyases; C031581:cytochrome C synthetase