Fig. 1.

The β₂AR-G protein signaling pathways. (A) The agonist-bound β₂AR activates either G_s or G_i heterotrimer, which stimulates or inhibits the adenylyl cyclase activity, respectively. (B) Structure of β₂AR-Gs complex (PDB ID code: 3SN6), the lysine residues that are chosen as NMR probes are shown as solid spheres, other lysine residues were mutated to arginine as described in the text. (C–E) The lysine probes undergo conformational changes during the activation of the β₂AR, as shown by cytoplasmic views of active β₂AR (PDB ID code: 3SN6) (C), inactive β₂AR (PDB ID code: 2RH1) (D), and the overlap of active and inactive β₂AR (E).