Figure 6.

Schematic state diagram for Cl⁻ transport cycle in the CmCLC. (A) Deprotonated E210 blocks Cl⁻ translocation from S_ext to S_cen. (B) Protonation of E210 opens the GLU_ex gate. (C) One Cl⁻ ion transports to and occupies the S_cen site. (D) Two Cl⁻ ions reside in the S_cen site and a continuous water wire is formed from the S_cen site to the extracellular solution. (E) Deprotonation of the GLU_ex gate drives two Cl⁻ ions to the intracellular side. The cycle thus returns to its initial state A. Cl⁻ ions are shown as spheres (cyan). Each picture is taken from MD snapshots of different simulation systems. For simplification, only residues E210, Y515, and S165 are shown in licorice format and waters within 12 Å of E210 are shown in CPK format. Oxygen (red), nitrogen (blue), carbon (cyan), and hydrogen (white) atoms are colored differently. States A and E have deprotonated GLU_ex and states B, C, and D have protonated GLU_ex. (Color online.)