Fig. 2: NMR spectra of isoprenaline-bound β₁AR-E show the receptor populating an active state that differs in its structure from the ternary complex with mini-G_s.

a The positions of the assigned ¹H-¹³C and ¹⁹F NMR probes are mapped onto the structure of β₁AR in ternary complex with isoprenaline and activating nanobody (PDB: 6H7J) where they are indicated as coloured spheres: ¹³C methyl groups of the native methionine residues (blue), introduced methionine L289M^6.34 (green), ¹⁹F TET probe conjugated to the native cysteine C344^7.54 (orange) and the ¹⁹F BTFA probe conjugated to cysteine A282C^6.27 (red) (Figure made with PyMol V2.4.1). b–d Superposition of 2D ¹H-¹³C HMQC correlation spectra with assignments indicated for β₁AR-E in the ligand free apo state (orange), in the active state bound to isoprenaline (purple) and in ternary complex bound to isoprenaline and mini-G_s (blue). The enlarged view in (d) shows the signal response of L289M^6.34 on TM6 upon stepwise receptor activation of β₁AR-E-L289M^6.34. For guidance, sizeable changes in chemical shift upon activation are indicated by black arrows. The individual peak centres are indicated by dots. e 1D ¹⁹F NMR spectra of β₁AR-E labelled at ^TETC344^7.54 on TM7 showing the apo receptor (orange), the isoprenaline-bound active state (purple) and the ternary complex of β₁AR bound to isoprenaline and mini-G_s (blue). A known degradation peak is indicated by an asterisk.