Biochemical requirements for the maturation of mitochondrial c-type cytochromes.
Cytochromes c are metalloproteins that function in electron transfer reactions and contain a heme moiety covalently attached via thioether linkages between the co-factor and a CXXCH motif in the protein. Covalent attachment of the heme group occurs on the positive side of all energy-transducing membranes (bacterial periplasm, mitochondrial intermembrane space and thylakoid lumen) and requires minimally: 1) synthesis and translocation of the apocytochromes c and heme across at least one biological membrane, 2) reduction of apocytochromes c and heme and maintenance under a reduced form prior to 3) catalysis of the heme attachment reaction. Surprisingly, the conversion of apoforms of cytochromes c to their respective holoforms occurs through at least three different pathways (systems I, II and III). In this review, we detail the assembly process of soluble cytochrome c and membrane-bound cytochrome c1, the only two mitochondrial c-type cytochromes that function in respiration. Mitochondrial c-type cytochromes are matured in the intermembrane space via the system I or system III pathway, an intriguing finding considering that the biochemical requirements for cytochrome c maturation are believed to be common regardless of the energy-transducing membrane under study.
Hamel
Patrice
P
Department of Plant Cellular and Molecular Biology, The Ohio State University, 43210, Columbus, OH 43210, USA. hamel.16@osu.edu
Corvest
Vincent
V
Giegé
Philippe
P
Bonnard
Géraldine
G
D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D010084:Oxidation-Reduction
D001059:Apoproteins; D024101:Mitochondrial Proteins; D006418:Heme; D045304:Cytochromes c