Figure 2.

Ba²⁺ binding in the open-gate wt KcsA structures. (A) Side view of the open-gate wt KcsA soaked in 1 mM BaCl₂/5 mM KCl. Two diagonally opposing monomers are shown for clarity. Ba²⁺ (magenta sphere) is shown binding in the selectivity filter. (B) Close view of the selectivity filter in the region Thr74–Asp80. Anomalous Fourier difference map (orange mesh) for Ba⁺² contoured at 8 σ, and F_o − F_c map (green mesh) contoured at 6 σ.