Figure 5.

Potentials of mean force for Cl⁻ transport from the S_ext site to the intracellular solution in the protonated GLU_ex system (A_pB_p system). The single ion PMF is shown via a black line. Gray line represents the PMF for transport of one Cl⁻ ion from S_cen to intracellular solution with another Cl⁻ bound to the S_ext site. The position of the bound Cl⁻ is indicated by a solid circle in the figure. In the PMF calculations, the bound Cl⁻ ion is restrained using an isotropic three-dimensional harmonic restraint (with force constant of 1.0 kcal·mol⁻¹·Å⁻²) at the external binding site S_ext suggested by the crystal structure (PDB: 3ORG).