Fig. 5.

Structural features and common activation mechanism of class A GPCRs. a Ligand-binding pockets. Agonist, antagonist, and allosteric ligand are indicated as sticks in yellow, green, and salmon, respectively. Ligands are shown from the following structures (PDB code): 2RH1, 3PWH, 3VW7, 4IAR, 4MQT, 4PHU, 4RWS, 4XEE, 4XNV, 4Z35, and 4ZJ8. b–f The common activation pathway of class A GPCRs as exampled by the structures of inactive (gray, PDB code 3NYA) and active β₂AR (green, PDB code 3SN6). The conformational changes of conserved “micro-switches”, including CWxP (b), PIF (c), Na⁺ pocket (d), NPxxY (e), and DRY (f), are highlighted. Side chains of residues in “micro-switches” are shown as sticks. Red arrows indicate the shift and swing directions of elements in the active β₂AR structure relative to the inactive one