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J Cell Biol. 2017 Jan 2;216(1):83-92. doi: 10.1083/jcb.201607066. Epub 2016 Dec 23.

Two distinct membrane potential-dependent steps drive mitochondrial matrix protein translocation.

Author information

1
Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
2
Department of Molecular Biology, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany.
3
Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91190 Gif-sur-Yvette, France.
4
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.
5
Institute of Biochemistry and Molecular Biology, Center for Biochemistry and Molecular Cell Research, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
6
Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany.
7
Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany Peter.Rehling@medizin.uni-goettingen.de.
8
Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.

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.

PMID:
28011846
PMCID:
PMC5223606
DOI:
10.1083/jcb.201607066
[Indexed for MEDLINE]
Free PMC Article

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