Fig. 4.

Analysis of extracellular residues of class A G protein-coupled receptors. (A) Multiple sequence alignment of several class A G protein-coupled receptors. βAR=β-adrenergic receptor, AAR=adenosine receptor, DR=dopamine receptor, MR=muscarinic acetylcholine receptor. (B) Structural alignment of β₂-adrenergic receptor (β₂AR, tan) and β₁-adrenergic receptor (β₁AR, yellow, PDB: 7BTS). β₂AR residue F193 and β₁AR residue F201 are indicated by sticks. (C) β-arrestin recruitment to wild-type β₁AR (β₁AR-WT) and β₁AR-F201A as measured by bioluminescence resonance energy transfer (BRET). Human embryonic kidney 293cells co-transfected with β-arrestin2-GFP10 and indicated β₁AR-WT-RlucII or β₁AR-F201A-RlucII constructs were incubated with coelenterazine 400a for 2 minutes and then stimulated with indicated concentrations of isoproterenol (ISO). Data were collected at 6 minutes post agonist addition. n = 3 independent experiments. (E) Dose response curves for ISO promoted mini-G_s recruitment to β₁AR by BRET. Human embryonic kidney 293cells transiently transfected wild-type or mutated β₁AR-Rluc and NES-Venus-mGs were stimulated with the indicated concentrations of ISO for 15 minutes and BRET signal was measured. n = 3 independent experiments.