title: Gating the selectivity filter in ClC chloride channels.
abstract: ClC channels conduct chloride (Cl-) ions across cell membranes and thereby govern the electrical activity of muscle cells and certain neurons, the transport of fluid and electrolytes across epithelia, and the acidification of intracellular vesicles. The structural basis of ClC channel gating was studied. Crystal structures of wild-type and mutant Escherichia coli ClC channels bound to a monoclonal Fab fragment reveal three Cl- binding sites within the 15-angstrom neck of an hourglass-shaped pore. The Cl- binding site nearest the extracellular solution can be occupied either by a Cl- ion or by a glutamate carboxyl group. Mutations of this glutamate residue in Torpedo ray ClC channels alter gating in electrophysiological assays. These findings reveal a form of gating in which the glutamate carboxyl group closes the pore by mimicking a Cl- ion.
authors.affiliation: Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: Raimund
authors.initials: R
authors.lastname: Dutzler
authors.forename: Ernest B
authors.initials: EB
authors.lastname: Campbell
authors.forename: Roderick
authors.initials: R
authors.lastname: MacKinnon
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001665:Binding Sites; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005971:Glutamates / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D015640:Ion Channel Gating; D008958:Models, Molecular; D009865:Oocytes; D018408:Patch-Clamp Techniques; D017354:Point Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014101:Torpedo; D014981:Xenopus
chemical_list: D000911:Antibodies, Monoclonal; C120501:CLC-0 chloride channel protein, Torpedo californica; D018118:Chloride Channels; D002712:Chlorides; D029968:Escherichia coli Proteins; D005971:Glutamates; D007140:Immunoglobulin Fab Fragments