An energy transduction mechanism used in bacterial flagellar type III protein export
Tohru Minamino, Yusuke V. Morimoto, Noritaka Hara & Keiichi Namba
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Nature Communications 2, Article number: 475 doi:10.1038/ncomms1488
Received 14 March 2011 Accepted 22 August 2011 Published 20 September 2011
Abstract
Flagellar proteins of bacteria are exported by a specific export apparatus. FliI ATPase forms a complex with FliH and FliJ and escorts export substrates from the cytoplasm to the export gate complex, which is made up of six membrane proteins. The export gate complex utilizes proton motive force across the cytoplasmic membrane for protein translocation, but the mechanism remains unknown. Here we show that the export gate complex by itself is a proton–protein antiporter that uses the two components of proton motive force, Δψ and ΔpH, for different steps of the protein export process. However, in the presence of FliH, FliI and FliJ, a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH–FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus.
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