title: The isolated voltage sensing domain of the Shaker potassium channel forms a voltage-gated cation channel.
abstract: Domains in macromolecular complexes are often considered structurally and functionally conserved while energetically coupled to each other. In the modular voltage-gated ion channels the central ion-conducting pore is surrounded by four voltage sensing domains (VSDs). Here, the energetic coupling is mediated by interactions between the S4-S5 linker, covalently linking the domains, and the proximal C-terminus. In order to characterize the intrinsic gating of the voltage sensing domain in the absence of the pore domain, the Shaker Kv channel was truncated after the fourth transmembrane helix S4 (Shaker-iVSD). Shaker-iVSD showed significantly altered gating kinetics and formed a cation-selective ion channel with a strong preference for protons. Ion conduction in Shaker-iVSD developed despite identical primary sequence, indicating an allosteric influence of the pore domain. Shaker-iVSD also displays pronounced 'relaxation'. Closing of the pore correlates with entry into relaxation suggesting that the two processes are energetically related.
authors.affiliation: Department of Physics, Université de Montréal, Montréal, Canada.|Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada.
authors.forename: Juan
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Physics, Université de Montréal, Montréal, Canada.|Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada.
authors.forename: Rikard
authors.identifier: 0000-0003-4484-2907
authors.initials: R
authors.lastname: Blunck
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072417:Protein Domains; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D014982:Xenopus laevis; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D051637:Shaker Superfamily of Potassium Channels; D015032:Zinc
keywords: D. melanogaster; biophysics; gating; mode-shift; potassium channel; structural biology; voltage sensor; voltage-clamp fluorometry; xenopus