Fig. 8

Surface electrostatics of AQP8 models. The slightly tilted side views show clear differences in potential between the C loop side (top) and the opposing side. Red areas represent relatively negative surfaces, while blue are positive. The approximate position of the membrane is shown by vertical lines and the central axis of the tetramer (dashed line), is indicated on HsAQP8. Note the negative surface deep in the membrane on the right of all models except the salmon AQP8b. This charge is due to an aspartate which corresponds to an asparagine in AtTIP2;1 and SsAQP8b, hence the aspartate is more likely to be in a protonated state in this hydrophobic environment. The vacuum electrostatics for individual monomers were generated in PyMOL [40] and are only for relative comparisons within the individual monomer as the scale varies between monomers