Fig. 7.

Cl⁻ binding sites observed in BEST1 are absent in prokaryotic KpBest. Structures are depicted similarly to Fig. 5A with two subunits shown. Cl⁻ binding sites (magenta spheres, the three sites for each subunit are shown) in BEST1 (Left) are located at the N-terminal ends of α-helices. KpBest (Right) has continuous α-helices in the corresponding locations (arrows) and does not contain these sites. Ca²⁺ ions in BEST1 are depicted as teal spheres.