title: Evolutionarily conserved intracellular gate of voltage-dependent sodium channels.
abstract: Members of the voltage-gated ion channel superfamily (VGIC) regulate ion flux and generate electrical signals in excitable cells by opening and closing pore gates. The location of the gate in voltage-gated sodium channels, a founding member of this superfamily, remains unresolved. Here we explore the chemical modification rates of introduced cysteines along the S6 helix of domain IV in an inactivation-removed background. We find that state-dependent accessibility is demarcated by an S6 hydrophobic residue; substituted cysteines above this site are not modified by charged thiol reagents when the channel is closed. These accessibilities are consistent with those inferred from open- and closed-state structures of prokaryotic sodium channels. Our findings suggest that an intracellular gate composed of a ring of hydrophobic residues is not only responsible for regulating access to the pore of sodium channels, but is also a conserved feature within canonical members of the VGIC superfamily.
authors.affiliation: 1] Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53706, USA [2] Molecular Pharmacology Graduate Program, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Oelstrom
authors.affiliation: Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Marcel P
authors.initials: MP
authors.lastname: Goldschen-Ohm
authors.affiliation: Molecular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Holmgren
authors.affiliation: Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Baron
authors.initials: B
authors.lastname: Chanda
mesh_terms: D000818:Animals; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D004594:Electrophysiology; D019143:Evolution, Molecular; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D051663:Kv1.2 Potassium Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D051381:Rats; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D061566:Voltage-Gated Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D051663:Kv1.2 Potassium Channel; D009124:Muscle Proteins; C466180:Scn4a protein, rat; D015222:Sodium Channels; D061566:Voltage-Gated Sodium Channels; D003545:Cysteine