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Drug-bound and -free outward-facing structures of a multidrug ABC exporter point to a swing mechanism

Chaptal, v.; Zampieri, V.; Wiseman, B.; Orelle, C.; Martin, J.; Nguyen, K.-A.; Magnard, S.; Gobet, A.; Di cesare, M.; Javed, W.; Kilburg, A.; Peuchmaur, M.; Marcoux, J.; Hogbom, M.; Jault, J.-M.; Boumendjel, A.; Falson, P. G.

2021-03-12 biochemistry
10.1101/2021.03.12.435132 bioRxiv
Show abstract

Multidrug ABC transporters translocate drugs across membranes by a mechanism for which the molecular features of drug release are so far unknown. Here, we resolved two ATP-Mg2+-bound outward-facing (OF) conformations of the Bacillus subtilis (homodimeric) BmrA, one by X-ray crystallography without drug, and another by single-particle cryo-EM with rhodamine 6G (R6G). Two R6G molecules bind to the drug-binding cavity at the level of the outer leaflet, between transmembrane (TM) helices 1-2 of one monomer and TM5-6 of the other. R6G induces a rearrangement of TM1-2, highlighting a flexibility that was confirmed by H/D exchange and molecular dynamics simulations. The latter also shows a fast post-release occlusion of the cavity driven by hydrophobicity. Altogether, these data support a new swing mechanism for drug transport.

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