ClC chloride channels viewed through a transporter lens.

Since its discovery, the ClC family of chloride channels has presented biophysicists with unexpected behaviours and unusual surprises. The latest of these is the realization that not only does the family feature genuine chloride channels, it also includes proton-coupled chloride transporters, which move chloride ions and protons across the membrane in opposite directions. The crystal structure of such a transporter serves as a useful platform for understanding ClC channels, and features of chloride/proton exchange-transport may provide a key for comprehending voltage-dependent gating of the channels.