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Tom70 enhances mitochondrial preprotein import efficiency by binding to internal targeting sequences.

Authors
  • Backes, Sandra1
  • Hess, Steffen1
  • Boos, Felix1
  • Woellhaf, Michael W1
  • Gödel, Sabrina2
  • Jung, Martin3
  • Mühlhaus, Timo4
  • Herrmann, Johannes M5
  • 1 Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany. , (Germany)
  • 2 Computational Systems Biology, University of Kaiserslautern, Kaiserslautern, Germany. , (Germany)
  • 3 Medical Biochemistry, Saarland University, Homburg, Germany. , (Germany)
  • 4 Computational Systems Biology, University of Kaiserslautern, Kaiserslautern, Germany [email protected] , (Germany)
  • 5 Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany [email protected] , (Germany)
Type
Published Article
Journal
The Journal of Cell Biology
Publisher
The Rockefeller University Press
Publication Date
Apr 02, 2018
Volume
217
Issue
4
Pages
1369–1382
Identifiers
DOI: 10.1083/jcb.201708044
PMID: 29382700
Source
Medline
License
Unknown

Abstract

The biogenesis of mitochondria depends on the import of hundreds of preproteins. N-terminal matrix-targeting signals (MTSs) direct preproteins to the surface receptors Tom20, Tom22, and Tom70. In this study, we show that many preproteins contain additional internal MTS-like signals (iMTS-Ls) in their mature region that share the characteristic properties of presequences. These features allow the in silico prediction of iMTS-Ls. Using Atp1 as model substrate, we show that iMTS-Ls mediate the binding to Tom70 and have the potential to target the protein to mitochondria if they are presented at its N terminus. The import of preproteins with high iMTS-L content is significantly impaired in the absence of Tom70, whereas preproteins with low iMTS-L scores are less dependent on Tom70. We propose a stepping stone model according to which the Tom70-mediated interaction with internal binding sites improves the import competence of preproteins and increases the efficiency of their translocation into the mitochondrial matrix.

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