Fig. 3: Transport pathway.

a, d The ion transport pathway in AtCLCa-Cl⁻(a) and AtCLCa-NO₃⁻ (d) protomer. Protomers are shown in side view with CBS domains hidden. NTD and TMD are colored orange and blue, respectively. The αI–J loop is colored red. The bifurcated ion transport pathways are shown as solid surface, green for Cl⁻ (a) or NO₃⁻ (d) transport pathway and yellow for H⁺ transport pathway, calculated by Caver⁵⁸. b, e A zoom-in view of the bifurcated ion transport pathway of AtCLCa-Cl⁻(b) and AtCLCa-NO₃⁻ (e) at the same magnification, displayed as meshes. Arrows indicate the direction of ion transport in the physiological state. Cl⁻ (b) and NO₃⁻ (e) are shown as spheres. Three critical residues near the pathway are shown as sticks. c, f Anion-binding sites. Cl⁻ (c) and NO₃⁻ (f) are shown as spheres and balls and sticks, respectively. Hydrogen bonds are shown as black dashed lines.