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TOM, the entry gate of mitochondria

Structure and functional steps of the main entry gate of the cellular powerhouses have been solved in a collaboration of Japanese and Freiburg research teams

The cellular powerhouses (mitochondria) are essential for life and possess more than 1,000 different proteins. Most mitochondrial proteins are synthesized as precursors in the cytosol and have to be imported into the powerhouses. The translocase of the outer membrane (TOM complex) forms the entry gate for >90% of the precursor proteins. The exact structure and mode of operation of the TOM complex have been unknown.


In a collaboration of Japanese research teams around Toshiya Endo (Kyoto) and the Freiburg research teams of Nils Wiedemann, Thomas Becker und Nikolaus Pfanner from the Institute of Biochemistry and Molecular Biology, a detailed structure-function analysis of the TOM complex has been achieved and published in the journal Nature. The TOM complex consists of two channels, several receptors and small subunits. The import channels harbor at least two different transport routes: one for hydrophilic proteins with cleavable signal sequences and one for hydrophobic proteins with internal signals. Thus, the sorting of precursor proteins occurs already at the level of the TOM complex that transfers the precursor to further transport complexes of the mitochondria.


The TOM complex not only forms the entry gate of the powerhouses, but is also a crucial sorting hub to promote the proper transfer of precursor proteins to their functional destinations inside mitochondria.


Original Publication:


Araiso, Y., Tsutsumi, A., Qiu, J., Imai, K., Shiota, T., Song, J., Lindau, C., Wenz, L.S., Sakaue, H., Yunoki, K., Kawano, S., Suzuki, J., Wischnewski, M., Schütze, C., Ariyama, H., Ando, T., Becker, T., Lithgow, T., Wiedemann, N., Pfanner, N., Kikkawa, M., and Endo, T. (2019). Structure of the mitochondrial import gate reveals distinct preprotein paths. Nature, epub October 10, 2019, doi: 10.1038/s41586-019-1680-7




Professor Nils Wiedemann

Institute of Biochemistry and Molecular Biology

Faculty of Medicine

University of Freiburg

Phone: +49 761 203 5280