Fig. 1

The five positions of the selectivity filter in EcAqpZ and in AtTIP2;1.The five amino acid residues shown in stick representation in EcAqpZ (a) and AtTIP2;1 (b) are used to describe the selectivity filter. The positions of these amino acids in the selectivity filter are named according to their localization in secondary structural elements: helix 2 (H2^P), loop C (LC^P), helix 5 (H5^P), loop E (LE^P), and helix E (HE^P). Cartoon representation of the backbone with rainbow coloring, N- and C-terminal ends are blue and red, respectively. Oxygens of two water molecules in the selectivity filter are shown as red spheres