Figure 2. Conservation of the intramembrane Na⁺ ion and associated water network in β₁AR and A_2AR.

An alignment between cyanopindolol-bound β₁AR (PDB code 4BVN) and ZM241385-bound A_2AR (PDB code 4EIY) [38] was performed and the positions of waters (small spheres), Na⁺ ions (large spheres) and ligands (sticks) compared superposed on the surface of representation of β₁AR (grey): purple, β₁AR; cyan, A_2AR. The last two digits for the number of each water molecule in β₁AR is shown in the bottom inset. The alignment was performed based on the polar side chains in the solvent channel that are conserved between β₁AR and A_2AR (β₁AR/A_2AR: N339/284^7.49, N59/24^1.50, D87/52^2.50, S128/91^3.39, N335/280^7.45, Ser336/281^7.46, W303/246^6.48) with an overall RMSD of 0.30 for 30 atoms.