1.A.8.6.3
Aquaporin, Aqy1 (PIP2-7 7).  The subangstron (0.88Å) structure is available (Kosinska Eriksson et al. 2013).  the H-bond donor interactions of the NPA motif''s asparagine residues to passing water molecules are revealed. A polarized water-water H-bond configuration is observed within the channel.  Four selectivity filter water positions are too closely spaced to be simultaneously occupied. Strongly correlated movements break the connectivity of selectivity filter water molecules to other water molecules within the channel, thereby preventing proton transport via a Grotthuss mechanism.