Probing the Effects of Gating on the Ion Occupancy of the K+ Channel Selectivity Filter Using Two-Dimensional Infrared Spectroscopy

• DOI: 10.1021/jacs.7b01594
• Publication Date: 2017-05-05T07:48:01Z
• Authors: Huong T. Kratochvil; Michał Maj; Kimberly Matulef; Alvin W. Annen; Jared Ostmeyer; Eduardo Perozo; Benoît Roux; Francis I. Valiya...; Martin T. Zanni
• Keywords: KcsA potassium channel

The interplay between the intracellular gate and selectivity filter underlies structural basis for gating in potassium ion channels. Using a combination of protein semisynthesis, two-dimensional infrared (2D IR) spectroscopy, molecular dynamics (MD) simulations, we probe occupancy at S1 binding site constricted state KcsA channel when is open closed. 2D IR spectra resolve two features, whose relative intensities depend on gate. By matching experiment to calculated structures predicted by MD identify features as corresponding states with occupied or unoccupied K+. We learn that >70% closed <15% open. Comparison trajectories show opening causes change filter, which leads occupancy. This work reveals complexity conformational landscape K+ its dependence