title: Voltage-dependent proton transport by the voltage sensor of the Shaker K+ channel.
abstract: In voltage-dependent ion channels, pore opening is initiated by electrically driven movements of charged residues, and this movement generates a gating current. To examine structural rearrangements in the Shaker K+ channel, basic residues R365 and R368 in the S4 segment were replaced with histidine, and gating currents were recorded. Changes in gating charge displacement with solvent pH reveal voltage-dependent changes in exposure of the histidine to solvent protons. This technique directly monitors accessibility changes during gating, probes the environment even in confined locations, and introduces minimal interference of gating charge motion. The results indicate that charges 365 and 368 traverse the entire electric field during gating. The remarkable implication of the successive exposure of histidine to each side of the membrane is that in a pH gradient, the voltage sensor transports protons.
authors.affiliation: Department of Physiology, UCLA School of Medicine, Los Angeles, California 90095, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Starace
authors.forename: E
authors.initials: E
authors.lastname: Stefani
authors.forename: F
authors.initials: F
authors.lastname: Bezanilla
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D016384:Consensus Sequence; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D007700:Kinetics; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D017354:Point Mutation; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D051637:Shaker Superfamily of Potassium Channels
chemical_list: D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels; D006639:Histidine; D008536:Meglumine