Powering the ABC multidrug exporter LmrA: How nucleotides embrace the ion-motive force.
Lau, Calvin HF
Khoo, Yvonne SK
Nair, Asha V
Deery, Michael J
American Association for the Advancement of Science (AAAS)
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Agboh, K., Lau, C. H., Khoo, Y. S., Singh, H., Raturi, S., Nair, A. V., Howard, J., et al. (2018). Powering the ABC multidrug exporter LmrA: How nucleotides embrace the ion-motive force.. Sci Adv, 4 (9), eaas9365. https://doi.org/10.1126/sciadv.aas9365
LmrA is a bacterial ATP-binding cassette (ABC) multidrug exporter that uses metabolic energy to transport ions, cytotoxic drugs, and lipids. Voltage clamping in a Port-a-Patch was used to monitor electrical currents associated with the transport of monovalent cationic HEPES+ by single-LmrA transporters and ensembles of transporters. In these experiments, one proton and one chloride ion are effluxed together with each HEPES+ ion out of the inner compartment, whereas two sodium ions are transported into this compartment. Consequently, the sodium-motive force (interior negative and low) can drive this electrogenic ion exchange mechanism in cells under physiological conditions. The same mechanism is also relevant for the efflux of monovalent cationic ethidium, a typical multidrug transporter substrate. Studies in the presence of Mg-ATP (adenosine 5'-triphosphate) show that ion-coupled HEPES+ transport is associated with ATP-bound LmrA, whereas ion-coupled ethidium transport requires ATP binding and hydrolysis. HEPES+ is highly soluble in a water-based environment, whereas ethidium has a strong preference for residence in the water-repelling plasma membrane. We conclude that the mechanism of the ABC transporter LmrA is fundamentally related to that of an ion antiporter that uses extra steps (ATP binding and hydrolysis) to retrieve and transport membrane-soluble substrates from the phospholipid bilayer.
Lactobacillus, Sodium, Magnesium, HEPES, Ethidium, Lipid Bilayers, Phospholipids, Bacterial Proteins, Multidrug Resistance-Associated Proteins, Recombinant Proteins, Adenosine Triphosphate, Patch-Clamp Techniques, Drug Resistance, Bacterial, Binding Sites, Hydrogen-Ion Concentration
This research was supported by the Biotechnology and Biological Sciences Research Council grants BB/R00224X/1, BB/I002383/1 and BB/K017713/1, and Medical Research Council grant G0401165 (to H.W.V.V.). We are also grateful for funding by the Human Frontier Science Program (grant RGP0034/2013), Strategic International Cooperative Program (Japan Science and Technology Agency, Japan) and Royal Society (UK) for collaborative research between H.W.V.V. and S.M. C.H.F.L. received a research studentship of Peterhouse, Cambridge. Y.S.K.K. received a Federal Training Award from the Ministry of Health in Malaysia. H.S. and S.R. were supported by the Cambridge Commonwealth, European and International Trust.
Biotechnology and Biological Sciences Research Council (BB/I002383/1)
Royal Society (2010/R1)
Medical Research Council (G0401165)
Biotechnology and Biological Sciences Research Council (BB/K017713/1)
Human Frontier Science Program (HFSP) (RPG0034/2013)
Biotechnology and Biological Sciences Research Council (BB/R00224X/1)
Medical Research Council (MC_PC_13059)
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External DOI: https://doi.org/10.1126/sciadv.aas9365
This record's URL: https://www.repository.cam.ac.uk/handle/1810/280495
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/