Haem-polypeptide interactions during cytochrome c maturation.
Cytochrome c maturation involves the translocation of a polypeptide, the apocytochrome, and its cofactor, haem, through a membrane, before the two molecules are ligated covalently. This review article focuses on the current knowledge on the journey of haem during this process, which is known best in the Gram-negative bacterium Escherichia coli. As haem always occurs bound to protein, its passage across the cytoplasmic membrane and incorporation into the apocytochrome appears to be mediated by a set of proteinaceous maturation factors, the Ccm (cytochrome c maturation) proteins. At least three of them, CcmC, CcmE and CcmF, are thought to interact directly with haem. CcmE binds haem covalently, thus representing an intermediate of the haem trafficking pathway. CcmC is required for binding of haem to CcmE, and CcmF for releasing it from CcmE and transferring it onto the apocytochrome. The mechanism by which haem crosses the cytoplasmic membrane is currently unknown.
Thöny-Meyer
L
L
Institute of Microbiology, ETH Zürich, Schmelzbergstrasse 7, CH-8092, Zürich, Switzerland. lthoeny@micro.biol.ethz.ch
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins; D000458:Cyanobacteria; D003574:Cytochrome c Group / Q000737:chemistry* / Q000235:genetics; D045304:Cytochromes c; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006418:Heme / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae
D001059:Apoproteins; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C492058:CcmC protein, E coli; C116246:CcmC protein, bacteria; C115384:CcmE protein, E coli; D003574:Cytochrome c Group; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D008565:Membrane Proteins; D006418:Heme; D045304:Cytochromes c