title: CCME, a nuclear-encoded heme-binding protein involved in cytochrome c maturation in plant mitochondria.
abstract: The maturation of c-type cytochromes requires the covalent attachment of the heme cofactor to the apoprotein. For this process, plant mitochondria follow a pathway distinct from that of animal or yeast mitochondria, closer to that found in alpha- and gamma-proteobacteria. We report the first characterization of a nuclear-encoded component, namely AtCCME, the Arabidopsis thaliana orthologue of CcmE, a periplasmic heme chaperone in bacteria. AtCCME is targeted to mitochondria, and its N-terminal signal peptide is cleaved upon import. AtCCME is a peripheral protein of the mitochondrial inner membrane, and its major hydrophilic domain is oriented toward the intermembrane space. Although a AtCCME (Met(79)-Ser(256)) is not fully able to complement an Escherichia coli CcmE mutant strain for bacterial holocytochrome c production, it is able to bind heme covalently through a conserved histidine, a feature previously shown for E. coli CcmE. Our results suggest that AtCCME is important for cytochrome c maturation in A. thaliana mitochondria and that its heme-binding function has been conserved evolutionary between land plant mitochondria and alpha-proteobacteria.
authors.affiliation: Institut de Biologie Moléculaire des Plantes du CNRS, Université Louis Pasteur, 12 rue du Général Zimmer, F-67084 Strasbourg, France.
authors.forename: N
authors.initials: N
authors.lastname: Spielewoy
authors.forename: H
authors.initials: H
authors.lastname: Schulz
authors.forename: J M
authors.initials: JM
authors.lastname: Grienenberger
authors.forename: L
authors.initials: L
authors.lastname: Thony-Meyer
authors.forename: G
authors.initials: G
authors.lastname: Bonnard
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins; D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000235:genetics; D016764:Cell Polarity; D003574:Cytochrome c Group / Q000378:metabolism*; D018628:Gene Dosage; D006418:Heme / Q000378:metabolism*; D006420:Hemeproteins / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; C422944:CCME protein, Arabidopsis; D003574:Cytochrome c Group; D006420:Hemeproteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D006418:Heme