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J Bacteriol. 2010 Sep;192(17):4498-503. doi: 10.1128/JB.00334-10. Epub 2010 Jun 25.

Functional relationships between the AcrA hairpin tip region and the TolC aperture tip region for the formation of the bacterial tripartite efflux pump AcrAB-TolC.

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Department of Life Science (BK21 Program), Chung-Ang University, Seoul, Republic of Korea.


Tripartite efflux pumps found in Gram-negative bacteria are involved in antibiotic resistance and toxic-protein secretion. In this study, we show, using site-directed mutational analyses, that the conserved residues located in the tip region of the alpha-hairpin of the membrane fusion protein (MFP) AcrA play an essential role in the action of the tripartite efflux pump AcrAB-TolC. In addition, we provide in vivo functional data showing that both the length and the amino acid sequence of the alpha-hairpin of AcrA can be flexible for the formation of a functional AcrAB-TolC pump. Genetic-complementation experiments further indicated functional interrelationships between the AcrA hairpin tip region and the TolC aperture tip region. Our findings may offer a molecular basis for understanding the multidrug resistance of pathogenic bacteria.

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