The non-canonical mitochondrial inner membrane presequence translocase of trypanosomatids contains two essential rhomboid-like proteins
Anke Harsman, Silke Oeljeklaus, Christoph Wenger, Jonathan L. Huot, Bettina Warscheid & André Schneider
Nature Communications 7, Article number: 13707 (2016)
Mitochondria Protein translocation Proteomics
Received: 07 April 2016 Accepted: 24 October 2016 Published online: 19 December 2016
Mitochondrial protein import is essential for all eukaryotes. Here we show that the early diverging eukaryote Trypanosoma brucei has a non-canonical inner membrane (IM) protein translocation machinery. Besides TbTim17, the single member of the Tim17/22/23 family in trypanosomes, the presequence translocase contains nine subunits that co-purify in reciprocal immunoprecipitations and with a presequence-containing substrate that is trapped in the translocation channel. Two of the newly discovered subunits are rhomboid-like proteins, which are essential for growth and mitochondrial protein import. Rhomboid-like proteins were proposed to form the protein translocation pore of the ER-associated degradation system, suggesting that they may contribute to pore formation in the presequence translocase of T. brucei. Pulldown of import-arrested mitochondrial carrier protein shows that the carrier translocase shares eight subunits with the presequence translocase. This indicates that T. brucei may have a single IM translocase that with compositional variations mediates import of presequence-containing and carrier proteins.
A.H. gratefully acknowledges a fellowship from the Peter und Traudl Engelhorn foundation. We thank B. Knapp for technical assistance in LC-MS analyses. Research in the group of B.W. was funded by the Deutsche Forschungsgemeinschaft and the Excellence Initiative of the German Federal and State Governments (EXC 294 BIOSS Centre for Biological Signalling Studies). Research in the laboratory of A.S. was supported by grant 138355 and in part by the NCCR ‘RNA & Disease’ both funded by the Swiss National Science Foundation. Deposition of the data to the ProteomeXchange Consortium was supported by the PRIDE Team, EBI.
Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland
Anke Harsman, Christoph Wenger, Jonathan L. Huot & André Schneider
Department of Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestraße 18, Freiburg 79104, Germany
Silke Oeljeklaus & Bettina Warscheid
BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestraße 18, Freiburg 79104, Germany
A.H. and A.S. designed the experiments. A.H., C.W. and J.L.H. performed and analysed the experiments. Quantitative proteomic experiments were designed by S.O. and B.W. and SILAC-MS data were collected and analysed by S.O. A.S. and B.W. supervised the project. A.S. coordinated the entire project and obtained the main source of funding; A.H. and A.S. prepared and revised the manuscript with the input of S.O. and B.W.
The authors declare no competing financial interests.
Correspondence to Bettina Warscheid or André Schneider.