Potassium channel selectivity filter dynamics revealed by single-molecule FRET

Shizhen Wang, Sun Joo Lee, Grigory Maksaev, Xin Fang, Chong Zuo, Colin G. Nichols

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Potassium (K) channels exhibit exquisite selectivity for conduction of K + ions over other cations, particularly Na + . High-resolution structures reveal an archetypal selectivity filter (SF) conformation in which dehydrated K + ions, but not Na + ions, are perfectly coordinated. Using single-molecule FRET (smFRET), we show that the SF-forming loop (SF-loop) in KirBac1.1 transitions between constrained and dilated conformations as a function of ion concentration. The constrained conformation, essential for selective K + permeability, is stabilized by K + but not Na + ions. Mutations that render channels nonselective result in dilated and dynamically unstable conformations, independent of the permeant ion. Further, while wild-type KirBac1.1 channels are K + selective in physiological conditions, Na + permeates in the absence of K + . Moreover, whereas K + gradients preferentially support 86 Rb + fluxes, Na + gradients preferentially support 22 Na + fluxes. This suggests differential ion selectivity in constrained versus dilated states, potentially providing a structural basis for this anomalous mole fraction effect.

Original languageEnglish
Pages (from-to)377-383
Number of pages7
JournalNature Chemical Biology
Volume15
Issue number4
DOIs
StatePublished - Apr 1 2019

Fingerprint Dive into the research topics of 'Potassium channel selectivity filter dynamics revealed by single-molecule FRET'. Together they form a unique fingerprint.

Cite this