1. Structure and mechanism of the K+/H+ exchanger KefC.
- Author
-
Gulati, Ashutosh, Kokane, Surabhi, Perez-Boerema, Annemarie, Alleva, Claudia, Meier, Pascal F., Matsuoka, Rei, and Drew, David
- Subjects
POTASSIUM channels ,ESCHERICHIA coli ,MOLECULAR structure ,ION channels ,GRAM-negative bacteria ,CELL survival ,POTASSIUM - 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. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF