The TOM core complex: the general protein import pore of the outer membrane of mitochondria |
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| Authors: | Ahting U Thun C Hegerl R Typke D Nargang F E Neupert W Nussberger S |
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| Affiliation: | aInstitut für Physiologische Chemie der Universität München, D-80336 München, Germany; bAbteilung für Molekulare Strukturbiologie, Max-Planck Institut für Biochemie, D-82152 Martinsried, Germany; cDepartment of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada |
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| Abstract: | Translocation of nuclear-encoded preproteins across the outer membrane of mitochondria is mediated by the multicomponent transmembrane TOM complex. We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside. It consists of Tom40, Tom22, and the small Tom components, Tom6 and Tom7. This core complex was also purified directly from mitochondria after solubilization with dodecyl maltoside. The TOM core complex has the characteristics of the general insertion pore; it contains high-conductance channels and binds preprotein in a targeting sequence-dependent manner. It forms a double ring structure that, in contrast to the holo complex, lacks the third density seen in the latter particles. Three-dimensional reconstruction by electron tomography exhibits two open pores traversing the complex with a diameter of approximately 2.1 nm and a height of approximately 7 nm. Tom40 is the key structural element of the TOM core complex. |
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| Keywords: | TOM complex mitochondria protein translocation channel electron tomography protein targeting |
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