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Mol Microbiol. 2008 Oct;70(2):311-22. doi: 10.1111/j.1365-2958.2008.06402.x. Epub 2008 Aug 22.

Assembly of the translocase motor onto the preprotein-conducting channel.

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Institute of Molecular Biology and Biotechnology-FoRTH, PO Box 1385, Iraklio, Crete, Greece.


Bacterial protein secretion is catalysed by the SecYEG protein-conducting channel complexed with the SecA ATPase motor. To gain insight into the SecA-SecYEG interaction we used peptide arrays, thermodynamic quantification, mutagenesis and functional assays. Our data reveal that: (i) SecA binds with low affinity on several, peripheral, exposed SecYEG sites. This largely electrostatic association is modulated by temperature and nucleotides. (ii) Binding sites cluster in five major binding 'regions': three that are exclusively cytoplasmic and two that reach the periplasm. (iii) Both the N-terminal and c-terminal regions of SecA participate in binding interactions and share some sites. (iv) Several of these sites are essential for translocase catalysis. Our data provide residue-level dissection of the SecYEG-SecA interaction. Two models of assembly of SecA on dimeric SecYEG are discussed.

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