title: Two distinct membrane potential-dependent steps drive mitochondrial matrix protein translocation.
abstract: Two driving forces energize precursor translocation across the inner mitochondrial membrane. Although the membrane potential (Δψ) is considered to drive translocation of positively charged presequences through the TIM23 complex (presequence translocase), the activity of the Hsp70-powered import motor is crucial for the translocation of the mature protein portion into the matrix. In this study, we show that mitochondrial matrix proteins display surprisingly different dependencies on the Δψ. However, a precursor's hypersensitivity to a reduction of the Δψ is not linked to the respective presequence, but rather to the mature portion of the polypeptide chain. The presequence translocase constituent Pam17 is specifically recruited by the receptor Tim50 to promote the transport of hypersensitive precursors into the matrix. Our analyses show that two distinct Δψ-driven translocation steps energize precursor passage across the inner mitochondrial membrane. The Δψ- and Pam17-dependent import step identified in this study is positioned between the two known energy-dependent steps: Δψ-driven presequence translocation and adenosine triphosphate-driven import motor activity.
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
authors.forename: Alexander Benjamin
authors.identifier: http://orcid.org/0000-0003-3360-9130
authors.initials: AB
authors.lastname: Schendzielorz
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0001-7189-2518
authors.initials: C
authors.lastname: Schulz
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
authors.forename: Oleksandr
authors.identifier: http://orcid.org/0000-0003-1032-2612
authors.initials: O
authors.lastname: Lytovchenko
authors.affiliation: Department of Molecular Biology, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Clancy
authors.affiliation: Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91190 Gif-sur-Yvette, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaire, Centre de Biologie Intégrative, Université de Toulouse, Centre National de la Recherche Scientifique, Unité Propre de Service, 31062 Toulouse, France.|Institute of Biochemistry and Molecular Biology, Center for Biochemistry and Molecular Cell Research, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Ieva
authors.affiliation: Institute of Biochemistry and Molecular Biology, Center for Biochemistry and Molecular Cell Research, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.|Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
authors.affiliation: Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany Peter.Rehling@medizin.uni-goettingen.de.|Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
authors.forename: Peter
authors.identifier: http://orcid.org/0000-0001-5661-5272
authors.initials: P
authors.lastname: Rehling
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D005838:Genotype; D006868:Hydrolysis; D053078:Membrane Potential, Mitochondrial; D008565:Membrane 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; D009154:Mutation; D010641:Phenotype; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; C503873:Pam17 protein, S cerevisiae; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; C469615:TIM50 protein, S cerevisiae; D000255:Adenosine Triphosphate