title: Calibrated measurement of gating-charge arginine displacement in the KvAP voltage-dependent K+ channel.
abstract: Voltage-dependent ion channels open and conduct ions in response to changes in cell-membrane voltage. The voltage sensitivity of these channels arises from the motion of charged arginine residues located on the S4 helices of the channel's voltage sensors. In KvAP, a prokaryotic voltage-dependent K+ channel, the S4 helix forms part of a helical hairpin structure, the voltage-sensor paddle. We have measured the membrane depth of residues throughout the KvAP channel using avidin accessibility to different-length tethered biotin reagents. From these measurements, we have calibrated the tether lengths and derived the thickness of the membrane that forms a barrier to avidin penetration, allowing us to determine the magnitude of displacement of the voltage-sensor paddles during channel gating. Here we show that the voltage-sensor paddles are highly mobile compared to other regions of the channel and transfer the gating-charge arginines 15-20 A through the membrane to open the pore.
authors.affiliation: Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, New York 10021, USA.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Ruta
authors.forename: Jiayun
authors.initials: J
authors.lastname: Chen
authors.forename: Roderick
authors.initials: R
authors.lastname: MacKinnon
mesh_terms: D001120:Arginine / Q000737:chemistry*; D001360:Avidin / Q000737:chemistry; D001710:Biotin / Q000737:chemistry; D004560:Electricity; D015640:Ion Channel Gating; D008051:Lipid Bilayers / Q000737:chemistry*; D008954:Models, Biological; D008958:Models, Molecular; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D008051:Lipid Bilayers; D024642:Potassium Channels, Voltage-Gated; D001360:Avidin; D001710:Biotin; D001120:Arginine