The Mitochondrial Import Complex MIM Functions as Main Translocase for α-Helical Outer Membrane Proteins.

The mitochondrial outer membrane contains integral proteins with α-helical membrane anchors or a transmembrane β-barrel. The translocase of the outer membrane (TOM) cooperates with the sorting and assembly machinery (SAM) in the import of β-barrel proteins, whereas the mitochondrial import (MIM) complex inserts precursors of multi-spanning α-helical proteins. Single-spanning proteins constitute more than half of the integral outer membrane proteins; however, their biogenesis is poorly understood. We report that the yeast MIM complex promotes the insertion of proteins with N-terminal (signal-anchored) or C-terminal (tail-anchored) membrane anchors. The MIM complex exists in three dynamic populations. MIM interacts with TOM to accept precursor proteins from the receptor Tom70. Free MIM complexes insert single-spanning proteins that are imported in a Tom70-independent manner. Finally, coupling of MIM and SAM promotes early assembly steps of TOM subunits. We conclude that the MIM complex is a major and versatile protein translocase of the mitochondrial outer membrane. Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.

Citation

Kim Nguyen Doan, Alexander Grevel, Christoph U Mårtensson, Lars Ellenrieder, Nicolas Thornton, Lena-Sophie Wenz, Łukasz Opaliński, Bernard Guiard, Nikolaus Pfanner, Thomas Becker. The Mitochondrial Import Complex MIM Functions as Main Translocase for α-Helical Outer Membrane Proteins. Cell reports. 2020 Apr 28;31(4):107567

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PMID: 32348752

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