Fig. 4: The middle of the β2AR-[CT] interacts with the cytoplasmic surface of the β2AR.

a A schematic model of SrtA ligation of the ¹⁵N isotopic labeled β₂AR-[CT]. The SrtA ligation site was introduced at the end of H8 (see supplementary Fig 1a). The inactive β₂AR structure (PDB ID: 2RH1) is shown in the grey cartoon, while the active structure is shown in the green cartoon (PDB ID: 3P0G). b The sequence of the β₂AR-[CT] labeled for NMRs studies. The red text highlights the negatively charged residues that show chemical shift changes in panel c. c The weighted average ¹H–¹⁵N chemical shift changes (Δδ_av) and intensity ratio for each ¹⁵N β₂AR-[CT] residue (347-413) in the absence and presence of Gs protein. Weighted average ¹H–¹⁵N chemical shift changes were calculated as Δδ_av  =  ((Δδ_H)²  +  (Δδ_N/5)²)^1/2. The intensity ratio was calculated as I_R-Gs/I_R. Dots on the curve indicate two sequential 8 h of measurements of spectra and the merged spectrum. d The spectra of agonist-β₂AR-[CT]-Gs complex is more similar to the spectra of MBP-[CT] than the β₂AR-[CT]. Representative peaks from superposed ¹H–¹⁵N HSQC spectra of ¹⁵N MBP-[CT], BI occupied ¹⁵N β₂AR-[CT], and BI occupied ¹⁵N β₂AR-[CT] coupled to nucleotide-free Gs. The peak centers are shown as colored circles.