Instantaneous ion configurations in the K+ ion channel selectivity filter revealed by 2D IR spectroscopy

TitleInstantaneous ion configurations in the K+ ion channel selectivity filter revealed by 2D IR spectroscopy
Publication TypeJournal Article
Year of Publication2016
AuthorsKratochvil H.T., Carr J.K, Matulef K., Annen A.W., Li H., Maj M., Ostmeyer J., Serrano A L., Raghuraman H., Moran S.D, Skinner JL, Perozo E., Roux B., Valiyaveetil F.I., Zanni M T.
Secondary TitleScience
Volume353
Issue6303
Pagination1040-1044
Date Published09/2016
PublisherScience
Abstract

Potassium channels are responsible for the selective permeation of K+ ions across cell membranes. K+ ions permeate in single file through the selectivity filter, a narrow pore lined by backbone carbonyls that compose four K+ binding sites. Here, we report on the two-dimensional infrared (2D IR) spectra of a semisynthetic KcsA channel with site-specific heavy (13C18O) isotope labels in the selectivity filter. The ultrafast time resolution of 2D IR spectroscopy provides an instantaneous snapshot of the multi-ion configurations and structural distributions that occur spontaneously in the filter. Two elongated features are resolved, revealing the statistical weighting of two structural conformations. The spectra are reproduced by molecular dynamics simulations of structures with water separating two K+ ions in the binding sites, ruling out configurations with ions occupying adjacent sites.

URLhttp://science.sciencemag.org/content/353/6303/1040
DOI10.1126/science.aag1447