title: Organization of the mitochondrial translation machinery studied in situ by cryoelectron tomography.
abstract: Whereas the structure and function of cytosolic ribosomes have been studied in great detail, we know surprisingly little about the structural basis of mitochondrial protein synthesis. Here we used cryoelectron tomography and subtomogram analysis to visualize mitoribosomes in isolated yeast mitochondria, avoiding perturbations during ribosomal purification. Most mitoribosomes reside in immediate proximity to the inner mitochondrial membrane, in line with their specialization in the synthesis of hydrophobic membrane proteins. The subtomogram average of membrane-associated mitoribosomes reveals two distinct membrane contact sites, formed by the 21S rRNA expansion segment 96-ES1 and the inner membrane protein Mba1. On the basis of our data, we further hypothesize that Mba1 is not just a passive mitoribosome receptor on the inner membrane, but that it spatially aligns mitoribosomes with the membrane insertion machinery. This study reveals detailed insights into the supramolecular organization of the mitochondrial translation machinery and its association with the inner membrane in translation-competent mitochondria.
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Pfeffer
authors.affiliation: Cell Biology, University of Kaiserslautern, Erwin-Schrodinger-Strasse 13, 67663 Kaiserslautern, Germany.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Woellhaf
authors.affiliation: Cell Biology, University of Kaiserslautern, Erwin-Schrodinger-Strasse 13, 67663 Kaiserslautern, Germany.
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Herrmann
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Förster
mesh_terms: D020285:Cryoelectron Microscopy; D003600:Cytosol / Q000378:metabolism; D003576:Electron Transport Complex IV; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins; D014176:Protein Biosynthesis; D012335:RNA, Ribosomal / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D015003:Yeasts / Q000502:physiology
chemical_list: C454219:21S rRNA; C100490:MBA1 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D012335:RNA, Ribosomal; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV