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Plant nodulin-26 intrinsic proteins (NIPs) are members of the aquaporin superfamily that serve as multifunctional transporters of uncharged metabolites. In Arabidopsis thaliana, a specific NIP pore subclass, known as the NIP II proteins, is represented by AtNIP5;1 and AtNIP6;1, which encode channel proteins expressed in roots and leaf nodes, respectively, that participate in the transport of the critical cell wall nutrient boric acid. Modeling of the protein encoded by the AtNIP7;1 gene shows that it is a third member of the NIP II pore subclass in Arabidopsis. However, unlike AtNIP5;1 and AtNIP6;1 proteins, which form constitutive boric acid channels, AtNIP7;1 forms a channel with an extremely low intrinsic boric acid transport activity. Molecular modeling and molecular dynamics simulations of AtNIP7;1 suggest that a conserved tyrosine residue (Tyr81) located in transmembrane helix 2 adjacent to the aromatic arginine …