Figure 9.

Idealized potential occupation of the KcsA selectivity filter by Na⁺, Ba²⁺, K⁺, Cs⁺ and Rb⁺, in the presence or absence of TBA⁺ bound to the channel’s vestibule. Red crosses indicate nonconductive conformations for the selectivity filter under those experimental conditions. The PDB entries used for these models are: 2ITC (Na⁺), 2ITD (Ba²⁺), 1K4D (low K⁺), 2HVJ (low K⁺, TBA⁺), 1K4C (high K⁺), 2HVK (high K⁺, TBA⁺), 1R3L (Cs⁺) and 1R3I (Rb⁺).