Chloride channels and antiport mechanism

In a new paper in Journal of General Physiology, Brandeis postdoc Hyun-Ho Lim and Professor Christopher Miller examine the detailed mechanism by which a chloride transporter protein works. In particular, this protein does a rather crazy thing: it stoichiometrically swaps a proton on one side of the membrane for two Cl- ions on the other, and countertransports them across the membrane.  In this work, the authors identify a special glutamate residue on the cytoplasmic side of the protein that is responsible for picking up protons on that side in order to carry out this “antiport” mechanism.  (That glutamate is indicated by the spacefilled residue with red oxygen atoms in this depiction of the dimeric protein.)