High-pH structure of EmrE reveals the mechanism of proton-coupled substrate transport.

Autor: Shcherbakov AA; Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA., Spreacker PJ; Department of Biochemistry, University of Wisconsin at Madison, Madison, WI, 53706, USA., Dregni AJ; Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA., Henzler-Wildman KA; Department of Biochemistry, University of Wisconsin at Madison, Madison, WI, 53706, USA., Hong M; Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA. meihong@mit.edu.
Jazyk: angličtina
Zdroj: Nature communications [Nat Commun] 2022 Feb 18; Vol. 13 (1), pp. 991. Date of Electronic Publication: 2022 Feb 18.
DOI: 10.1038/s41467-022-28556-6
Abstrakt: The 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 H N -F distances for a fluorinated substrate, 4-fluoro-tetraphenylphosphonium (F 4 -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.
(© 2022. The Author(s).)
Databáze: MEDLINE
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