FIGURE 1.

NMR chemical shift comparison of wtTAR and TAR_m. (a) Secondary structures of wtTAR and TAR_m. Residues with the largest chemical shift perturbations (>0.25 ppm) between wtTAR and TAR_m are highlighted on the wtTAR secondary structure using solid black symbols. Apical loop residues that undergo significant chemical shift perturbations upon ARG binding are highlighted in open black symbols. See inset in c for symbol key. (b) 2D ¹H-¹³C HSQC spectra of wtTAR (red) overlaid on corresponding spectra of TAR_m (blue). Asterisks and colored labels denote resonances that are different between wtTAR and TAR_m due to the loop mutation. (c) Chemical shift differences ( where and are the changes in proton and carbon/nitrogen chemical shift and α is the ratio of the H and C/N gyromagnetic ratio) between wtTAR and TAR_m.