title: Congruent pattern of accessibility identifies minimal pore gate in a non-symmetric voltage-gated sodium channel.
abstract: Opening and closing of the central ion-conducting pore in voltage-dependent ion channels is gated by changes in membrane potential. Although a gate residue in the eukaryotic voltage-gated sodium channel has been identified, the minimal molecular determinants of this gate region remain unknown. Here, by measuring the closed- and open-state reactivity of MTSET to substituted cysteines in all the pore-lining helices, we show that the state-dependent accessibility is delineated by four hydrophobic residues at homologous positions in each domain. Introduced cysteines above these sites do not react with intracellular MTSET while the channels are closed and yet are rapidly modified while the channels are open. These findings, in conjunction with state-dependent metal cross-bridging, support the notion that the gate residues in each of the four S6 segments of the eukaryotic sodium channel form an occlusion for ions in the closed state and are splayed open on activation.
authors.affiliation: Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, 1111 Highland Avenue, Room 5505, WIMR Tower II, Madison, Wisconsin 53705, USA.|Department of Biomolecular Chemistry, School of Medicine and Public Health, 420 Henry Mall, Room 1135 Biochemistry Bldg, Madison, Wisconsin 53706, USA.|Molecular &Cellular Pharmacology Graduate Training Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Oelstrom
authors.affiliation: Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, 1111 Highland Avenue, Room 5505, WIMR Tower II, Madison, Wisconsin 53705, USA.|Department of Biomolecular Chemistry, School of Medicine and Public Health, 420 Henry Mall, Room 1135 Biochemistry Bldg, Madison, Wisconsin 53706, USA.
authors.forename: Baron
authors.identifier: http://orcid.org/0000-0003-4954-7034
authors.initials: B
authors.lastname: Chanda
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics; D000818:Animals; D057927:Hydrophobic and Hydrophilic Interactions; D015640:Ion Channel Gating; D009154:Mutation / Q000235:genetics; D016062:Porosity; D000072417:Protein Domains; D013997:Time Factors; D061566:Voltage-Gated Sodium Channels / Q000737:chemistry* / Q000235:genetics; D014982:Xenopus laevis; D015032:Zinc / Q000378:metabolism
chemical_list: D000596:Amino Acids; D061566:Voltage-Gated Sodium Channels; D015032:Zinc