Article
- The EMBO Journal (2007) 26, 2229 - 2239
- doi:10.1038/sj.emboj.7601673
Published online: 5 April 2007
Subject Categories:
The morphology proteins Mdm12/Mmm1 function in the major 
-barrel assembly pathway of mitochondria
Chris Meisinger1, Sylvia Pfannschmidt1,2, Michael Rissler1, Dusanka Milenkovic1, Thomas Becker1, Diana Stojanovski1, Matthew J Youngman3, Robert E Jensen3, Agnieszka Chacinska1, Bernard Guiard4, Nikolaus Pfanner1 and Nils Wiedemann1
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Freiburg, Germany
- Fakultät für Biologie, Universität Freiburg, Freiburg, Germany
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France
Correspondence to:
Nikolaus Pfanner,
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, Hermann-Herder-Stra
e 7, 79104 Freiburg, Germany. Tel.: +49 761 203 5224; Fax: +49 761 203 5261; E-mail: nikolaus.pfanner@biochemie.uni-freiburg.de
Received 10 November 2006; Accepted 13 March 2007
Abstract
The 
-barrel proteins of mitochondria are synthesized on cytosolic ribosomes. The proteins are imported by the translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM). It has been assumed that the SAMcore complex with the subunits Sam35, Sam37 and Sam50 represents the last import stage common to all -barrel proteins, followed by splitting in a Tom40-specific route and a route for other -barrel proteins. We have identified new components of the -barrel assembly machinery and show that the major -barrel pathway extends beyond SAMcore. Mdm12/Mmm1 function after SAMcore yet before splitting of the major pathway. Mdm12/Mmm1 have been known for their role in maintenance of mitochondrial morphology but we reveal assembly of -barrel proteins as their primary function. Moreover, Mdm10, which functions in the Tom40-specific route, can associate with SAMcore as well as Mdm12/Mmm1 to form distinct assembly complexes, indicating a dynamic exchange between the machineries governing mitochondrial -barrel assembly. We conclude that assembly of mitochondrial -barrel proteins represents a major function of the morphology proteins Mdm12/Mmm1.
Keywords:
- Mdm10,
- mitochondria,
- protein sorting,
- Saccharomyces cerevisiae,
- SAM complex
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The EMBO Journal Article (13 Dec 2006)
