Fig. 5

K⁺ binding at the cluster II Na site. a Structural comparison of the cluster II Na site between Na⁺-bound (left) and K⁺-bound (right) structures. Purple and green spheres represent Na⁺ and K⁺ ions, respectively. b Superimposition of the two structures. c Single channel recordings from an inside-out patch with 150 mM [Na⁺] in the pipette solution (extracellular) and 150 mM [Na⁺] or [K⁺] in the bath solution (intracellular). Replacing K⁺ with Na⁺ in the bath solution significantly reduced the single-channel open probability