title: Motor-free mitochondrial presequence translocase drives membrane integration of preproteins.
abstract: The mitochondrial inner membrane is the central energy-converting membrane of eukaryotic cells. The electrochemical proton gradient generated by the respiratory chain drives the ATP synthase. To maintain this proton-motive force, the inner membrane forms a tight barrier and strictly controls the translocation of ions. However, the major preprotein transport machinery of the inner membrane, termed the presequence translocase, translocates polypeptide chains into or across the membrane. Different views exist of the molecular mechanism of the translocase, in particular of the coupling with the import motor of the matrix. We have reconstituted preprotein transport into the mitochondrial inner membrane by incorporating the purified presequence translocase into cardiolipin-containing liposomes. We show that the motor-free form of the presequence translocase integrates preproteins into the membrane. The reconstituted presequence translocase responds to targeting peptides and mediates voltage-driven preprotein translocation, lateral release and insertion into the lipid phase. Thus, the minimal system for preprotein integration into the mitochondrial inner membrane is the presequence translocase, a cardiolipin-rich membrane and a membrane potential.
authors.affiliation: Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-StraSSe 7, D-79104 Freiburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
authors.forename: Michael
authors.initials: M
authors.lastname: Meinecke
authors.forename: Jan
authors.initials: J
authors.lastname: Dudek
authors.forename: Dana P
authors.initials: DP
authors.lastname: Hutu
authors.forename: Maria
authors.initials: M
authors.lastname: Lind
authors.forename: Inge
authors.initials: I
authors.lastname: Perschil
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.forename: Richard
authors.initials: R
authors.lastname: Wagner
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Pfanner
authors.forename: Peter
authors.initials: P
authors.lastname: Rehling
mesh_terms: D003575:Cytochromes c1 / Q000378:metabolism; D047468:Immunoprecipitation; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*