Fig. 3. Comparison of the receptor-coupling interfaces in the β₁AR_6P–βarr1 and β₂AR–G_s complexes.

a, Snake plot of the intracellular region of turkey β₁AR with amino acid residues colour-coded according to interactions: red, contact between β₁AR_6P and βarr1; blue, contact between β₂AR and G_s; purple, both contacts. b, c, Cross-sections through the intracellular halves of β₂AR (b) and β₁AR_6P (c) to highlight the different shapes of the intracellular cleft formed upon coupling of βarr1 compared with G_s. Transmembrane helices are shown for orientation, and are in front of the cross-section. d, Detail of the interface between the βarr1 finger loop (pale green) and β₁AR_6P (pale blue). e, Detail of the interface between the α5 helix of the G_s α-subunit (blue) and β₂AR (green). Depicted in d, e are polar interactions (red dashes), van der Waals interactions (blue dashes; atoms ≤ 3.9 Å apart) and Arg^3.50 (shown as sticks: carbon, grey).