Download MendeleyHigh-pH structure of EmrE reveals the mechanism of proton-coupled substrate transport.
Shcherbakov, A.A., Spreacker, P.J., Dregni, A.J., Henzler-Wildman, K.A., Hong, M.(2022) Nat Commun 13: 991-991
- PubMed: 35181664
- DOI: https://doi.org/10.1038/s41467-022-28556-6
- Primary Citation of Related Structures:
7SFQ - PubMed Abstract:
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.
Organizational Affiliation:
Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA, 02139, USA.
