Fig. 7

Rare NPP motif in salmon AQP8 changes the hydrogen bonding and widens the pore. In spite of the unusual NPP motif, the overall fold of the SsAQP8b model (salmon) is similar to the template AtTIP2;1 (green) harboring the canonical NPA motif. Nevertheless, the second proline in the NPP motif of SsAQP8b (P94) eliminates a hydrogen bond partner of the asparagine (N92), which instead turns to the next amide of the backbone (F95). The altered orientation of the asparagine widens the pore and potentially optimizes the polar interactions with the permeant substrate