Fig. 1.

The E71-D80 interaction is structurally analogous to the molecular bowstring in Kir channels and is disrupted in the E71A KcsA mutant. Images are taken from crystal structures of Kir2.2 (3JYC), KcsA (1K4C), and the flipped (yellow) and nonflipped (gray) structures of the E71A mutant of KcsA (1ZWI, 2ATK), showing the selectivity filter region from one subunit and highlighting the residues involved in a salt-bridge interaction in Kir2.2, and the hydrogen-bond interactions in KcsA. Black spheres represent potassium ions and the blue sphere represents water.