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- Title
Structure and mechanism of the K<sup>+</sup>/H<sup>+</sup> exchanger KefC.
- Authors
Gulati, Ashutosh; Kokane, Surabhi; Perez-Boerema, Annemarie; Alleva, Claudia; Meier, Pascal F.; Matsuoka, Rei; Drew, David
- Abstract
Intracellular potassium (K+) homeostasis is fundamental to cell viability. In addition to channels, K+ levels are maintained by various ion transporters. One major family is the proton-driven K+ efflux transporters, which in gram-negative bacteria is important for detoxification and in plants is critical for efficient photosynthesis and growth. Despite their importance, the structure and molecular basis for K+-selectivity is poorly understood. Here, we report ~3.1 Å resolution cryo-EM structures of the Escherichia coli glutathione (GSH)-gated K+ efflux transporter KefC in complex with AMP, AMP/GSH and an ion-binding variant. KefC forms a homodimer similar to the inward-facing conformation of Na+/H+ antiporter NapA. By structural assignment of a coordinated K+ ion, MD simulations, and SSM-based electrophysiology, we demonstrate how ion-binding in KefC is adapted for binding a dehydrated K+ ion. KefC harbors C-terminal regulator of K+ conductance (RCK) domains, as present in some bacterial K+-ion channels. The domain-swapped helices in the RCK domains bind AMP and GSH and they inhibit transport by directly interacting with the ion-transporter module. Taken together, we propose that KefC is activated by detachment of the RCK domains and that ion selectivity exploits the biophysical properties likewise adapted by K+-ion-channels. Intracellular potassium (K+) homeostasis is achieved by activity of both ion channels and transporters. Here, the authors report structures of E. coli glutathione (GSH)-gated K+ efflux transporter KefC with bound K+ and conclude that the ion-binding site is adapted for binding a dehydrated ion.
- Subjects
NAPA (Calif.); POTASSIUM channels; ESCHERICHIA coli; MOLECULAR structure; ION channels; GRAM-negative bacteria; CELL survival; POTASSIUM
- Publication
Nature Communications, 2024, Vol 15, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-024-49082-7