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Tripartite efflux pumps: energy is required for dissociation, but not assembly or opening of the outer membrane channel of the pump

Janganan, T.K.; Bavro, V.; Zhang, L.; Borges-Walmsley, M.I.; Walmsley, A.R.

Tripartite efflux pumps: energy is required for dissociation, but not assembly or opening of the outer membrane channel of the pump Thumbnail


Authors

T.K. Janganan

V. Bavro

L. Zhang

M.I. Borges-Walmsley

A.R. Walmsley



Abstract

The MtrCDE multidrug pump, from Neisseria gonorrhoeae, is assembled from the inner and outer membrane proteins MtrD and MtrE, which are connected by the periplasmic membrane fusion protein MtrC. Although it is clear that MtrD delivers drugs to the channel of MtrE, it remains unclear how drug delivery and channel opening are connected. We used a vancomycin sensitivity assay to test for opening of the MtrE channel. Cells expressing MtrE or MtrE-E434K were insensitive to vancomycin; but became moderately and highly sensitive to vancomycin respectively, when coexpressed with MtrC, suggesting that the MtrE channel opening requires MtrC binding and is energy-independent. Cells expressing wild-type MtrD, in an MtrCE background, were vancomycin-insensitive, but moderately sensitive in an MtrCE-E434K background. The mutation of residues involved in proton translocation inactivated MtrD and abolished drug efflux, rendered both MtrE and MtrE-E434K vancomycin-insensitive; imply that the pump-component interactions are preserved, and that the complex is stable in the absence of proton flux, thus sealing the open end of MtrE. Following the energy-dependent dissociation of the tripartite complex, the MtrE channel is able to reseal, while MtrE-E434K is unable to do so, resulting in the vancomycin-sensitive phenotype. Thus, our findings suggest that opening of the OMP via interaction with the MFP is energy-independent, while both drug export and complex dissociation require active proton flux.

Citation

Janganan, T., Bavro, V., Zhang, L., Borges-Walmsley, M., & Walmsley, A. (2013). Tripartite efflux pumps: energy is required for dissociation, but not assembly or opening of the outer membrane channel of the pump. Molecular Microbiology, 88(3), 590-602. https://doi.org/10.1111/mmi.12211

Journal Article Type Article
Acceptance Date Mar 19, 2013
Online Publication Date Apr 9, 2013
Publication Date May 1, 2013
Deposit Date Apr 30, 2013
Publicly Available Date Mar 28, 2024
Journal Molecular Microbiology
Print ISSN 0950-382X
Electronic ISSN 1365-2958
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 88
Issue 3
Pages 590-602
DOI https://doi.org/10.1111/mmi.12211

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
© 2013 The Authors. Molecular Microbiology Published by Blackwell Publishing Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.





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