tailieunhanh - Báo cáo khoa hoc : Cytochrome c maturation system on the negative side of bioenergetic membranes: CCB or System IV

Cytochromes of thec-type contain hemes covalently attached via one or, more generally, two thioether bonds between the vinyls of hemeband the thiols of cysteine residues of apocytochromes. This post-translational modi-fication relies on membrane-associated specific biogenesis proteins, referred to as cytochrome c maturation systems. | IFEBS Journal MINIREVIEW Cytochrome c maturation system on the negative side of bioenergetic membranes CCB or System IV Catherine de Vitry1 2 1 Centre Nationalde la Recherche Scientifique UMR 7141 Physiologie Membranaire et Moleculaire du Chloroplaste Institut de Biologie Physico-Chimique Paris France 2 Universite Pierre et Marie Curie Sorbonne Universites UMR 7141 Paris France Keywords biogenesis chloroplast c-type cytochrome heme photosynthesis Correspondence C. de Vitry CNRS UPMC UMR 7141 Institut de Biologie Physico-Chimique 13 Rue Pierre et Marie Curie 75005 Paris France Fax 33 0 1 58 41 50 55 Tel 33 0 1 58 41 50 22 E-mail Received 13 July 2011 revised 8 September 2011 accepted 16 September 2011 Cytochromes of the c-type contain hemes covalently attached via one or more generally two thioether bonds between the vinyls of heme b and the thiols of cysteine residues of apocytochromes. This post-translational modification relies on membrane-associated specific biogenesis proteins referred to as cytochrome c maturation systems. At least three different versions . Systems I-III are found on the positive side of bioenergetic membranes in different organisms and compartments. The present minireview is concerned with systems on the negative side of the membranes. It describes System IV also referred to as cofactor assembly on complex C subunit B for heme binding on cytochrome b6 through one thioether bond this covalent heme is usually called ci. This system is found in all organisms with oxygenic photosynthesis but not in Firmicutes although they also have a cytochrome b protein with an additional heme ci covalently attached via a single thioether bond. doi Introduction Cytochromes c are hemoproteins with covalently attached iron-protoporphyrin IX or heme b groups. They act as electron carriers such as in photosynthetic and respiratory electron transport chains as well as in a variety of other cellular .