title: CcmD is involved in complex formation between CcmC and the heme chaperone CcmE during cytochrome c maturation.
abstract: CcmD is a small membrane protein involved in heme delivery to the heme chaperone CcmE during cytochrome c maturation. Here we show that it physically interacts with CcmE and CcmC, another essential component of the heme delivery system. We demonstrate the formation of a ternary complex consisting of CcmCDE. A deletion analysis of individual domains revealed that the central hydrophobic domain is essential for its function. Moreover, the C-terminal, cytoplasmic domain seems to require a net positive charge to be functional. Our topology analysis indicates that CcmD is an integral interfacial membrane protein with its N and C termini extruding into the cytoplasmic side of the membrane. Interactions of CcmD with either ferrochelatase, the last heme biosynthetic enzyme, or directly with heme were not detectable. We postulate a function for CcmD in protein-protein interaction or membrane protein assembly required for the heme delivery process.
authors.affiliation: Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Str. 10, CH-8093 Zürich, Switzerland.
authors.forename: Umesh
authors.initials: U
authors.lastname: Ahuja
authors.forename: Linda
authors.initials: L
authors.lastname: Thöny-Meyer
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C116246:CcmC protein, bacteria; C415989:CcmD protein, E coli; C115384:CcmE protein, E coli; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D008565:Membrane Proteins; D006418:Heme; D045304:Cytochromes c