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Licensed Unlicensed Requires Authentication Published by De Gruyter May 14, 2015

Biogenesis of mitochondrial outer membrane proteins, problems and diseases

Lars Ellenrieder, Christoph U. Mårtensson and Thomas Becker
From the journal Biological Chemistry


Proteins of the mitochondrial outer membrane are synthesized as precursors on cytosolic ribosomes and sorted via internal targeting sequences to mitochondria. Two different types of integral outer membrane proteins exist: proteins with a transmembrane β-barrel and proteins embedded by a single or multiple α-helices. The import pathways of these two types of membrane proteins differ fundamentally. Precursors of β-barrel proteins are first imported across the outer membrane via the translocase of the outer membrane (TOM complex). The TOM complex is coupled to the sorting and assembly machinery (SAM complex), which catalyzes folding and membrane insertion of these precursors. The mitochondrial import machinery (MIM complex) promotes import of proteins with multiple α-helical membrane spans. Depending on the topology precursors of proteins with a single α-helical membrane anchor are imported via several distinct routes. We summarize current models and open questions of biogenesis of mitochondrial outer membrane proteins and discuss the impact of malfunctions of protein sorting on the development of diseases.

Corresponding author: Thomas Becker, Institute for Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, 79104 Freiburg, Germany; and BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany, e-mail:


We thank Dr. Lukasz Opaliński for discussion. This work was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 746, BE4679/2-1 and the Excellence Initiative of the German Federal and State Governments (EXC 294 BIOSS Centre for Biological Signalling Studies).


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Received: 2015-4-30
Accepted: 2015-5-8
Published Online: 2015-5-14
Published in Print: 2015-11-1

©2015 by De Gruyter

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