tailieunhanh - Báo cáo khoa hoc : Cytochrome c biogenesis in mitochondria – Systems III and V

In c-type cytochromes, heme becomes covalently attached to the polypep-tide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein. There are two such cytochromes in mitochondria: cytochromec and cytochromec1 . | IFEBS Journal REVIEW ARTICLE Cytochrome c biogenesis in mitochondria - Systems III and V James W. A. Allen Department of Biochemistry University of Oxford UK Keywords apoptosis cytochrome heme heme lyase holocytochrome c synthase microphthalmia with linear skin defects syndrome mitochondria post-translationalmodification trypanosome yeast Correspondence J. W. A. Allen Department of Biochemistry University of Oxford South Parks Road Oxford OX1 3QU UK Fax 44 0 1865 613201 Tel 44 0 1865 613330 E-mail Received 5 May 2011 revised 16 June 2011 accepted 4 July 2011 doi 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 c1. 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 c1 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. Introduction c-type cytochromes are characterized by covalent