Figure 4.

Water occupation map of the TM channel. (A) The channel formed across the TM domain of each receptor state using the 250 snapshots from 1000 to 1200 ns for the apo form, and from 600 to 800 ns for the agonist-bound and antagonist-bound forms, at which the highest water flux is observed. The channel surfaces, calculated using the program HOLE (55), are colored to visualize the channel radius (red (r < 1.15 Å), green (r = 1.15 ∼ 2.30 Å), and blue (r > 2.3 Å)). Channel radii (r) along the z axis are shown on the right with a different color for each frame. (B) Water occupancy maps along the axis perpendicular to the bilayer, calculated for the simulations of the apo (top), agonist- (middle), and antagonist-bound forms (bottom). The positions of two hydrophobic layers (HL1 and HL2) are marked with red arrows. The position of the lipid headgroup is in cyan lines on the map. A magnified view of the water occupation map for 600 ≲ t ≲ 800 ns is provided. On the right, the apo structure is displayed with the key microswitches. To see this figure in color, go online.