title: Structural dynamics of potassium-channel gating revealed by single-molecule FRET.
abstract: Crystallography has provided invaluable insights regarding ion-channel selectivity and gating, but to advance understanding to a new level, dynamic views of channel structures within membranes are essential. We labeled tetrameric KirBac1.1 potassium channels with single donor and acceptor fluorophores at different sites and then examined structural dynamics within lipid membranes by single-molecule fluorescence resonance energy transfer (FRET). We found that the extracellular region is structurally rigid in both closed and open states, whereas the N-terminal slide helix undergoes marked conformational fluctuations. The cytoplasmic C-terminal domain fluctuates between two major structural states, both of which become less dynamic and move away from the pore axis and away from the membrane in closed channels. Our results reveal mobile and rigid conformations of functionally relevant KirBac1.1 channel motifs, implying similar dynamics for similar motifs in eukaryotic Kir channels and in cation channels in general.
authors.affiliation: Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO.
authors.forename: Shizhen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL.
authors.forename: Reza
authors.initials: R
authors.lastname: Vafabakhsh
authors.affiliation: Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO.
authors.forename: William F
authors.initials: WF
authors.lastname: Borschel
authors.affiliation: Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL.|Howard Hughes Medical Institute, Baltimore, MD.|Department of Biophysics and Biophysical Chemistry, Department of Biophysics, Department of Biomedical Engineering, Baltimore, MD.
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
authors.affiliation: Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO.
authors.forename: Colin G
authors.initials: CG
authors.lastname: Nichols
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D007700:Kinetics; D008958:Models, Molecular; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D013194:Staining and Labeling / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D015221:Potassium Channels