Fig. 3: SF and hinge residues display ion-dependent chemical shifts.

Backbone amide (a) and ILV methyl (d) chemical shift perturbations (CSPs) along with ¹³C’ (c) and ¹³Cα (b) chemical shift differences (Δδ) were calculated for NaK in 100 mM K⁺ vs 600 mM Na⁺. CSPs (calculated as described in Methods) and Δδ values for residues assigned in both conditions are plotted against residue number. In each plot, the cyan line indicates 1.5σ above the 10% trimmed mean. CSPs and Δδ values are also plotted on the NaK structure (3E8H [10.2210/pdb3E8H/pdb], 2 adjacent of 4 subunits shown for clarity). Color scale bars are shown for each plot. ¹H–¹⁵N CSPs, ¹³C’ Δδ, and ¹³Cα Δδ values are plotted on the backbone and residues for which data are not available are colored gray. ¹H–¹³C_methyl CSPs are plotted on the side-chains and the backbone is shown in gray. Secondary structure elements are indicated on the plots and labeled on the structure in panel a.