Charge delocalization upon chloride ion binding in ClC chloride ion channels/transporters

► Significant charge delocalization for bound Cl− ions in ClC Cl− transport proteins. ► Important sinks of charges: Cl− solvation shells and the gating residue E148. ► Extensive anion-pi charge transfer found along the translocation path. ► An additional binding site for Cl− suggested by DFT geometry optimizations.