Mg2+-dependent mechanism of environmental versatility in a multidrug efflux pump

Russell Lewis, B.; Uddin, M. R.; Kuo, K. M.; Shah, L. M. N.; Harris, N. J.; Booth, P. J.; Hammerschmid, D.; Gumbart, J. C.; Zgurskaya, H. I.; Reading, E.

doi:10.1101/2024.06.10.597921

bioRxiv · 10.1101/2024.06.10.597921

Mg2+-dependent mechanism of environmental versatility in a multidrug efflux pump

Russell Lewis, B.·Uddin, M. R.·Kuo, K. M.·Shah, L. M. N.·Harris, N. J.·Booth, P. J.·Hammerschmid, D.·Gumbart, J. C.·Zgurskaya, H. I.·Reading, E.

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Abstract

Tripartite resistance nodulation and cell division multidrug efflux pumps span the periplasm and are a major driver of multidrug resistance among Gram-negative bacteria. The periplasm provides a distinct environment between the inner and outer membranes of Gram-negative bacteria. Cations, such as Mg2+, become concentrated within the periplasm and, in contrast to the cytoplasm, its pH is sensitive to conditions outside the cell. Here, we reveal an interplay between Mg2+ and pH in modulating the dynamics of the periplasmic adaptor protein, AcrA, and its function within the prototypical AcrAB-TolC multidrug efflux pump from Escherichia coli. In the absence of Mg2+, AcrA becomes increasingly plastic within acidic conditions, but when Mg2+ is bound this is ameliorated, resulting in domain specific organisation in neutral to weakly acidic regimes. We establish a unique histidine residue directs these structural dynamics and is essential for sustaining pump efflux activity across acidic, neutral, and alkaline conditions. Overall, we propose Mg2+ conserves the structural mobility of AcrA to ensure optimal AcrAB-TolC function within rapid changing environments commonly faced by the periplasm during bacterial infection and colonization. This work highlights that Mg2+ is an important mechanistic component in this pump class and possibly across other periplasmic lipoproteins.

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Russell Lewis, B., Uddin, M. R., Kuo, K. M., Shah, L. M. N., Harris, N. J., Booth, P. J., Hammerschmid, D., Gumbart, J. C., Zgurskaya, H. I., Reading, E.. 2024-06-10. Mg2+-dependent mechanism of environmental versatility in a multidrug efflux pump. https://doi.org/10.1101/2024.06.10.597921

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