Structural characterisation of a full-length mitochondrial outer membrane TOM40 preprotein translocase: implications for its interaction with presequence peptides
Tom40, the central component of the preprotein translocase of the mitochondrial outer membrane (TOM complex), forms the import pore that facilitates the translocation of preproteins across the outer membrane. Though the function of Tom40 has been intensively studied, the details of the interactions between presequence peptides and Tom40 remain unclear. In this study, we expressed rat Tom40 in Escherichia coli and purified it from inclusion bodies before investigating the refolded protein by fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The far-UV CD spectra of the refolded Tom40 in various concentrations of urea revealed that the refolded protein has a well-defined structure consisting mainly of β-sheet. Moreover, the specific binding of presequence peptides to Tom40, which was demonstrated by fluorescence quenching, showed that the refolded purified protein is functional and that the interaction between Tom40 and presequence peptides is mainly electrostatic in nature.
KeywordsMitochondria Tom40 Presequence peptides Refolding Interaction
This work was supported by National Natural Science Foundation of China (No. 30970579, 31271464 and 21707165), and the Ph.D. Programs Foundation of Ministry of Education of China (No. 20110031110004 and 20120031110028), and the Basic Science and Advance Technology Research Program of Tianjin (No. 14JCYBJC23400).
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Conflict of interest
The authors declare that they have no conflict of interest.
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