Figure 6.

The α345 hexamer crystal structure reveals crevices, pockets, and cavities along the surface and are solvent accessible.A, equatorial and meridian slices through the surface of the hexamer reveal a big central cavity going from one trimer to the other, small inner cavities encapsulating six chloride ions of group 1, and pockets accommodating six chloride ions of group 2. The central cavity contains multiple structured PEG molecules. Pockets also contain parts of PEG molecules. B, the same orientation of slices but shifted toward the crevices between chains and C4 subdomains. Interchain crevices are occupied by PEG molecules. Outside surface of the α345 hexamer is colored in light red for α3, light blue for α4, and light green for α5. The inner surface is colored in gray. Chloride ions of both group 1 and group 2 are shown as blue spheres. PEG molecules are shown as red wireframes. C, PEG molecules penetrate and surround the pockets with chloride ions. Coloring of the NC1 chains is light red for α3, light blue for α4, and light green for α5. Chloride ions of group 2 are shown as blue spheres. Structured PEG molecules are shown as red wireframes. Structured water molecules are shown as cyan spheres.