FIGURE 2.

The water channel in different simulations. The lipid bilayer is omitted for clarity. A, map of the water channel from Fig. 1 on the starting structure. Blue, main amino acids in contact with the water channel (see Table 2 for a list). B and C, comparison of water distribution in control MD simulations. B, c-ring with Glu⁶¹ of all 14 protomers protonated (uncharged). C, c-ring with all Glu⁶¹ deprotonated. Although the protonated ring (B) does not show a distinct water channel, a water ring is drawn toward the charged center of the c-ring (C). D–F, water channel in suppressor mutant cP24D/E61G. D, front view. The water channel developed from the top (n-side) to the one charged Asp²⁴. This channel is inclined to the vertical membrane normal and runs, as depicted here, from the top left to the center. E, top view. The water channel reaches as far as the carboxylate group of Asp²⁴. F, close-up view. The carboxylate group of Asp²⁴ establishes a hydrogen bond with the amide nitrogen of Gly⁶¹ with a distance of 3 Å. Gln²⁸ is hidden for clarity. A–D and F, top, n-side; bottom, p-side. A–C, spheres show Glu⁶¹ of c-protomers. D–F, spheres show cAsp²⁴. B–F, blue, water density at a contour level of 50 waters/ų over the course of the simulation. Black, inside of water density.