Binding of salmeterol to β₂AR.

<p><b>A.</b> Interactions of salmeterol at the binding site of an ANM-restrained-MD conformation; <b>B.</b> The location of salmeterol tail forming a ‘lid’ with the extracellular loop 2 (EC2) of β₂AR from the extracellular site view. The flexible tail of salmeterol folds parallel to the EC2 and stabilizes the rest of the ligand forming a lid at the extracellular site. The green arrow shows the direction that the salmeterol tail runs similar to a beta-sheet structure. <b>C.</b> The residues lining the salmeterol binding pocket; <b>D.</b> The stabilization of the aromatic ring of salmeterol by Val114, Thr118 at H3, Ser203 and Ser207 at H5, and Phe290 atH6. Carbon, oxygen, nitrogen and hydrogen atoms of salmeterol is colored green, red, blue and white; respectively. ANM-restrained-MD conformation that is able to accommodate inside the ligand binding pocket is shown in ribbon diagram with transparent helices. The residues with the majority of atoms within the 3.5 Å making specific interactions with salmeterol are displayed. The EC2 that closely interacts with salmeterol is also show in green ribbon diagram.