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April 4th, 2025
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University of Southampton
biochemistry
biorxiv

Molecular basis for multidrug efflux by an anaerobic RND transporter

Lawrence, R.Open in Google Scholar•Athar, M.Open in Google Scholar•Uddin, M. R.Open in Google Scholar•Adams, C.Open in Google Scholar•Sousa, J.Open in Google Scholar•Durrant, O.Open in Google Scholar•Lellman, S.Open in Google Scholar•Sutton, L.Open in Google Scholar•Keevil, C. W.Open in Google Scholar•Patel, N.Open in Google Scholaret al.

Bacterial efflux pumps provide resistance to antibiotics and toxic substances within demanding ecological settings, such as low oxygen, extreme acid, and during nutrient starvation. The MdtEF efflux pump from Escherichia coli is upregulated in these conditions and forms part of the proton motive force-driven resistance-nodulation-cell division (RND) superfamily. Here, we report cryo-electron microscopy structures of native lipid-contained multidrug exporter MdtF, including a single-point mutant with an altered multidrug phenotype and associated substrate-bound form. We reveal that drug binding domain and channel conformational plasticity likely govern its promiscuous substrate specificity, analogous to its closely related, constitutively expressed counterpart, AcrB. Whereas we discover distinct transmembrane state transitions within MdtF, which create a more engaged proton relay network, altered drug transport allostery and an acid-responsive increase in efflux efficiency. Physiologically, this equips bacteria with toxin and xenobiotic resistance during membrane remodelling that presage encounters with acid stresses, as experienced in the gastrointestinal tract.

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