Fig. 2
From: Shifts in the selectivity filter dynamics cause modal gating in K+ channels
Loss of the E71–D80 interaction causes extended rearrangements behind the filter. a Zoom into (left) 2D CC ssNMR spectra of WT KcsA (cyan), E71A (red), E71I (blue), and E71Q (orange) showing the D80 side chain CSPs. E71Q (right) mimics the E71–D80 interaction, which is lost in E71A and E71I. The D80 side chain CSPs are large in E71A and E71I, while they are small in E71Q. b Structural representation (1K4C) of the stabilisation of filter residues T74–G77 by hydrogen bonds with V70 and E71 of the pore helix. c The E71I turret is disordered, which causes signals to disappear or split. Spectral zooms are show for WT KcsA (cyan) and E71I (blue). d Overlay of 2D NH spectra showing a strong CSP for V70 of the pore helix. e Overlay of 2D CC spectra, showing CSPs of the functionally critical T74 side chain in E71X mutants. f The large T74 CSP in E71I (pH 7.4, 100 mM K+) is reminiscent of the inactivated filter in WT KcsA (pH 4, 0 mM K+)
