title: Cbp3-Cbp6 interacts with the yeast mitochondrial ribosomal tunnel exit and promotes cytochrome b synthesis and assembly.
abstract: Mitochondria contain their own genetic system to express a small number of hydrophobic polypeptides, including cytochrome b, an essential subunit of the bc(1) complex of the respiratory chain. In this paper, we show in yeast that Cbp3, a bc(1) complex assembly factor, and Cbp6, a regulator of cytochrome b translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial ribosomes and that exhibits two important functions in the biogenesis of cytochrome b. On the one hand, the interaction of Cbp3 and Cbp6 with mitochondrial ribosomes is necessary for efficient translation of cytochrome b transcript [corrected]. On the other hand, the Cbp3-Cbp6 complex interacts directly with newly synthesized cytochrome b in an assembly intermediate that is not ribosome bound and that contains the assembly factor Cbp4. Our results suggest that synthesis of cytochrome b occurs preferentially on those ribosomes that have the Cbp3-Cbp6 complex bound to their tunnel exit, an arrangement that may ensure tight coordination of cytochrome b synthesis and assembly.
authors.affiliation: Abteilung Membranbiogenese and 2 Abteilung Membranbiogenese Zellbiologie, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Steffi
authors.initials: S
authors.lastname: Gruschke
authors.forename: Kirsten
authors.initials: K
authors.lastname: Kehrein
authors.forename: Katharina
authors.initials: K
authors.lastname: Römpler
authors.forename: Kerstin
authors.initials: K
authors.lastname: Gröne
authors.forename: Lars
authors.initials: L
authors.lastname: Israel
authors.forename: Axel
authors.initials: A
authors.lastname: Imhof
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Herrmann
authors.forename: Martin
authors.initials: M
authors.lastname: Ott
mesh_terms: D045303:Cytochromes b / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D000637:Transaminases / Q000235:genetics / Q000378:metabolism
chemical_list: C435647:CBP3 protein, S cerevisiae; C088917:CBP4 protein, S cerevisiae; C561113:Cbp6 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D045303:Cytochromes b; D000637:Transaminases; C018731:acetylornithine transaminase