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J Cell Biol. 2017 Nov 6;216(11):3485-3495. doi: 10.1083/jcb.201706043. Epub 2017 Sep 15.

Identification of new channels by systematic analysis of the mitochondrial outer membrane.

Author information

1
Division of Biophysics, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany.
2
Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
3
BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
4
Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., Dortmund, Germany.
5
Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.
6
Institute of Biology II, Biochemistry - Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany.
7
Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany nikolaus.pfanner@biochemie.uni-freiburg.de.
8
Division of Biophysics, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany ri.wagner@jacobs-university.de.
9
Biophysics, Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany.

Abstract

The mitochondrial outer membrane is essential for communication between mitochondria and the rest of the cell and facilitates the transport of metabolites, ions, and proteins. All mitochondrial outer membrane channels known to date are β-barrel membrane proteins, including the abundant voltage-dependent anion channel and the cation-preferring protein-conducting channels Tom40, Sam50, and Mdm10. We analyzed outer membrane fractions of yeast mitochondria and identified four new channel activities: two anion-preferring channels and two cation-preferring channels. We characterized the cation-preferring channels at the molecular level. The mitochondrial import component Mim1 forms a channel that is predicted to have an α-helical structure for protein import. The short-chain dehydrogenase-related protein Ayr1 forms an NADPH-regulated channel. We conclude that the mitochondrial outer membrane contains a considerably larger variety of channel-forming proteins than assumed thus far. These findings challenge the traditional view of the outer membrane as an unspecific molecular sieve and indicate a higher degree of selectivity and regulation of metabolite fluxes at the mitochondrial boundary.

PMID:
28916712
PMCID:
PMC5674900
DOI:
10.1083/jcb.201706043
[Indexed for MEDLINE]
Free PMC Article

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