Figure 3.

Agonist binding site in the β₂AR. A. Amino acids involved in forming the agonist binding site for the β₂AR. The sites of interaction between catecholamines and the β₂AR have been extensively characterized [100–102]. The amine nitrogen interacts with Asp 113 in TM3 [103], the catechol hydroxyls interact with serines in TM5 [100–102]. Interactions with the aromatic ring and the chiral β-hydroxyl have both been mapped to TM6 [101]. B. A panel of β₂AR ligands discussed in this review. Catechol is a very weak partial agonist. Dopamine and salbutamol are partial agonists. Norepinephrine, epinephrine and isoproterenol are full agonists. ICI118,551 is an inverse agonist. D–E. Isoproterenol docked into a three-dimensional model of the β₂AR. Illustrations were made with MacPyMOL software.