High-pH structure of EmrE reveals the mechanism of proton-coupled substrate transport
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s41467-022-28556-6.pdf
Description
Published version
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3.12 MB
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Checksum (MD5)
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Author(s)
Shcherbakov, Alexander A
Spreacker, Peyton J
Dregni, Aurelio J
Henzler-Wildman, Katherine A
Hong, Mei
Date Issued
December 2022
Journal
Nature Communications
Publisher
Springer Science and Business Media LLC
Citation
Shcherbakov, Alexander A, Spreacker, Peyton J, Dregni, Aurelio J, Henzler-Wildman, Katherine A and Hong, Mei. 2022. "High-pH structure of EmrE reveals the mechanism of proton-coupled substrate transport." Nature Communications, 13 (1).
Version
Final published version
Abstract
AbstractThe homo-dimeric bacterial membrane protein EmrE effluxes polyaromatic cationic substrates in a proton-coupled manner to cause multidrug resistance. We recently determined the structure of substrate-bound EmrE in phospholipid bilayers by measuring hundreds of protein-ligand HN–F distances for a fluorinated substrate, 4-fluoro-tetraphenylphosphonium (F4-TPP+), using solid-state NMR. This structure was solved at low pH where one of the two proton-binding Glu14 residues is protonated. Here, to understand how substrate transport depends on pH, we determine the structure of the EmrE-TPP complex at high pH, where both Glu14 residues are deprotonated. The high-pH complex exhibits an elongated and hydrated binding pocket in which the substrate is similarly exposed to the two sides of the membrane. In contrast, the low-pH complex asymmetrically exposes the substrate to one side of the membrane. These pH-dependent EmrE conformations provide detailed insights into the alternating-access model, and suggest that the high-pH conformation may facilitate proton binding in the presence of the substrate, thus accelerating the conformational change of EmrE to export the substrate.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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Creative Commons Attribution 4.0 International license
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DOI of Published Version
https://doi.org/10.1038/s41467-022-28556-6
