Table 1. O–O distances at the edges of the water surrogating cages in the selectivity filter, Å
Selectivity filter edgeStructure (resolution)
KcsA 1K4C (2.0 Å)Kv1.2/2.1 2R9R (2.4 Å)MthK 4HYO (1.65 Å)KvAP 1ORQ (3.2 Å)
d13.63.53.54.1
d23.33.33.23.9
d33.33.33.33.9
d43.23.33.13.1
d53.73.93.63.4
h13.13.13.12.9
h23.03.03.02.7
h33.13.13.23.3
h43.02.92.92.9

Center to center inter-oxygen distances at the selectivity filter edges shown in Fig. 1 D. Distance calculations are directly from the Biological Assembly PDB file coordinates. Distances di result from the construction of the Biological Assembly. We chose the above structures because they showed the best resolution available at the time.