Fig. 3
Temperature dependence of chemical shifts and signal intensities in isoprenaline-bound β1AR-MetΔ5-L190M reveal a highly dynamic receptor. 2D 1H, 13C HMQC spectra (a) for the β1AR-MetΔ5-L190M construct recorded at 288 (blue), 298 (orange) and 308 K (red) showing the temperature dependence of the spectra. Resonance centres are indicated by coloured dots. All residues are seen to move with changing temperature, with substantial shifts for L190M and M1/M283, M223 and M296. Intensity changes are observed for M223 and M296 and at 298 K, M223 appears in two conformations (M223a and M223b). (Spectra were aligned using the isopropyl methyl group of unbound isoprenaline as a reference.) In b intensities, shown as signal-to-noise ratios (SNR), are plotted for M223 vs. M296 with uncorrected values in blue and corrected values accounting for the temperature and viscosity (η) changes (Supplementary Table 6) shown in orange. SNRs increase from 308 to 298 K indicating that at 308 K, M223 and M296 are in intermediate exchange leading to extensive peak broadening with a shift to slower exchange at lower temperatures, allowing separate states to be resolved as seen for M223 in a
