title: Heme Trafficking and Modifications during System I Cytochrome c Biogenesis: Insights from Heme Redox Potentials of Ccm Proteins.
abstract: Cytochromes c require covalent attachment of heme via two thioether bonds at conserved CXXCH motifs, a process accomplished in prokaryotes by eight integral membrane proteins (CcmABCDEFGH), termed System I. Heme is trafficked from inside the cell to outside (via CcmABCD) and chaperoned (holoCcmE) to the cytochrome c synthetase (CcmF/H). Purification of key System I pathway intermediates allowed the determination of heme redox potentials. The data support a model whereby heme is oxidized to form holoCcmE and subsequently reduced by CcmF/H for thioether formation, with Fe(2+) being required for attachment to CXXCH. Results provide insight into mechanisms for the oxidation and reduction of heme in vivo.
authors.affiliation: Department of Biology, Washington University , St. Louis, Missouri 63130, United States.
authors.forename: Molly C
authors.initials: MC
authors.lastname: Sutherland
authors.affiliation: Department of Biology, Washington University , St. Louis, Missouri 63130, United States.
authors.forename: Joel A
authors.initials: JA
authors.lastname: Rankin
authors.affiliation: Department of Biology, Washington University , St. Louis, Missouri 63130, United States.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Kranz
mesh_terms: D045304:Cytochromes c / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism*; D015151:Immunoblotting; D008190:Lyases / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D010084:Oxidation-Reduction; D021381:Protein Transport
chemical_list: D008565:Membrane Proteins; D018832:Molecular Chaperones; D006418:Heme; D045304:Cytochromes c; D008190:Lyases; C031581:cytochrome C synthetase