Figure 6.

Pictorial depiction of the paths of communication (OP/SOPs) from D133 in the ligand binding pocket to F139 at the Gs protein coupling interface for the (a) inactive and (b) active states of β2-AR. The path is blocked due to lack of appropriate interactions in the inactive state. Binding of Gs protein and agonist in the active state appears to re-establish this path of communication/signaling. The β2-AR and Gαs backbones are depicted in green and blue cartoon representation, respectively. The OP is shown in red and the SOPs are shown in blue lines. The source and the sink residues are highlighted as yellow van der Waals' spheres. The key F139 and Y141 residues and the ligand (inverse agonist/agonist) are shown in blue and violet stick representation, respectively. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]