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Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac
Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4113903/ https://www.ncbi.nlm.nih.gov/pubmed/25070432 http://dx.doi.org/10.1085/jgp.201411210 |
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author | Gamal El-Din, Tamer M. Scheuer, Todd Catterall, William A. |
author_facet | Gamal El-Din, Tamer M. Scheuer, Todd Catterall, William A. |
author_sort | Gamal El-Din, Tamer M. |
collection | PubMed |
description | Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine gating charges (R1–R3) with smaller amino acids allows ionic currents to flow through the mutant gating pore, and these gating pore currents are pathogenic in some skeletal muscle periodic paralysis syndromes. The voltage dependence of gating pore currents provides information about the transmembrane position of the gating charges as S4 moves in response to membrane potential. Here we studied gating pore current in mutants of the homotetrameric bacterial sodium channel NaChBac in which individual arginine gating charges were replaced by cysteine. Gating pore current was observed for each mutant channel, but with different voltage-dependent properties. Mutating the first (R1C) or second (R2C) arginine to cysteine resulted in gating pore current at hyperpolarized membrane potentials, where the channels are in resting states, but not at depolarized potentials, where the channels are activated. Conversely, the R3C gating pore is closed at hyperpolarized membrane potentials and opens with channel activation. Negative conditioning pulses revealed time-dependent deactivation of the R3C gating pore at the most hyperpolarized potentials. Our results show sequential voltage dependence of activation of gating pore current from R1 to R3 and support stepwise outward movement of the substituted cysteines through the narrow portion of the gating pore that is sealed by the arginine side chains in the wild-type channel. This pattern of voltage dependence of gating pore current is consistent with a sliding movement of the S4 helix through the gating pore. Through comparison with high-resolution models of the voltage sensor of bacterial sodium channels, these results shed light on the structural basis for pathogenic gating pore currents in periodic paralysis syndromes. |
format | Online Article Text |
id | pubmed-4113903 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-41139032015-02-01 Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac Gamal El-Din, Tamer M. Scheuer, Todd Catterall, William A. J Gen Physiol Research Articles Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine gating charges (R1–R3) with smaller amino acids allows ionic currents to flow through the mutant gating pore, and these gating pore currents are pathogenic in some skeletal muscle periodic paralysis syndromes. The voltage dependence of gating pore currents provides information about the transmembrane position of the gating charges as S4 moves in response to membrane potential. Here we studied gating pore current in mutants of the homotetrameric bacterial sodium channel NaChBac in which individual arginine gating charges were replaced by cysteine. Gating pore current was observed for each mutant channel, but with different voltage-dependent properties. Mutating the first (R1C) or second (R2C) arginine to cysteine resulted in gating pore current at hyperpolarized membrane potentials, where the channels are in resting states, but not at depolarized potentials, where the channels are activated. Conversely, the R3C gating pore is closed at hyperpolarized membrane potentials and opens with channel activation. Negative conditioning pulses revealed time-dependent deactivation of the R3C gating pore at the most hyperpolarized potentials. Our results show sequential voltage dependence of activation of gating pore current from R1 to R3 and support stepwise outward movement of the substituted cysteines through the narrow portion of the gating pore that is sealed by the arginine side chains in the wild-type channel. This pattern of voltage dependence of gating pore current is consistent with a sliding movement of the S4 helix through the gating pore. Through comparison with high-resolution models of the voltage sensor of bacterial sodium channels, these results shed light on the structural basis for pathogenic gating pore currents in periodic paralysis syndromes. The Rockefeller University Press 2014-08 /pmc/articles/PMC4113903/ /pubmed/25070432 http://dx.doi.org/10.1085/jgp.201411210 Text en © 2014 Gamal El-Din et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/). |
spellingShingle | Research Articles Gamal El-Din, Tamer M. Scheuer, Todd Catterall, William A. Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title | Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title_full | Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title_fullStr | Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title_full_unstemmed | Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title_short | Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac |
title_sort | tracking s4 movement by gating pore currents in the bacterial sodium channel nachbac |
topic | Research Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4113903/ https://www.ncbi.nlm.nih.gov/pubmed/25070432 http://dx.doi.org/10.1085/jgp.201411210 |
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