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K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels
Potassium channels allow the selective flux of K(+) excluding the smaller, and more abundant in the extracellular solution, Na(+) ions. Here we show that Shab is a typical K(+) channel that excludes Na(+) under bi-ionic, Na(o)/K(i) or Na(o)/Rb(i), conditions. However, when internal K(+) is replaced...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Public Library of Science
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4370708/ https://www.ncbi.nlm.nih.gov/pubmed/25798591 http://dx.doi.org/10.1371/journal.pone.0120431 |
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author | Carrillo, Elisa Pacheco, Lucero Balleza, Daniel Gomez-Lagunas, Froylan |
author_facet | Carrillo, Elisa Pacheco, Lucero Balleza, Daniel Gomez-Lagunas, Froylan |
author_sort | Carrillo, Elisa |
collection | PubMed |
description | Potassium channels allow the selective flux of K(+) excluding the smaller, and more abundant in the extracellular solution, Na(+) ions. Here we show that Shab is a typical K(+) channel that excludes Na(+) under bi-ionic, Na(o)/K(i) or Na(o)/Rb(i), conditions. However, when internal K(+) is replaced by Cs(+) (Na(o)/Cs(i)), stable inward Na(+) and outward Cs(+) currents are observed. These currents show that Shab selectivity is not accounted for by protein structural elements alone, as implicit in the snug-fit model of selectivity. Additionally, here we report the block of Shab channels by external Ca(2+) ions, and compare the effect that internal K(+) replacement exerts on both Ca(2+) and TEA block. Our observations indicate that Ca(2+) blocks the channels at a site located near the external TEA binding site, and that this pore region changes conformation under conditions that allow Na(+) permeation. In contrast, the latter ion conditions do not significantly affect the binding of quinidine to the pore central cavity. Based on our observations and the structural information derived from the NaK bacterial channel, we hypothesize that Ca(2+) is probably coordinated by main chain carbonyls of the pore´s first K(+)-binding site. |
format | Online Article Text |
id | pubmed-4370708 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-43707082015-04-04 K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels Carrillo, Elisa Pacheco, Lucero Balleza, Daniel Gomez-Lagunas, Froylan PLoS One Research Article Potassium channels allow the selective flux of K(+) excluding the smaller, and more abundant in the extracellular solution, Na(+) ions. Here we show that Shab is a typical K(+) channel that excludes Na(+) under bi-ionic, Na(o)/K(i) or Na(o)/Rb(i), conditions. However, when internal K(+) is replaced by Cs(+) (Na(o)/Cs(i)), stable inward Na(+) and outward Cs(+) currents are observed. These currents show that Shab selectivity is not accounted for by protein structural elements alone, as implicit in the snug-fit model of selectivity. Additionally, here we report the block of Shab channels by external Ca(2+) ions, and compare the effect that internal K(+) replacement exerts on both Ca(2+) and TEA block. Our observations indicate that Ca(2+) blocks the channels at a site located near the external TEA binding site, and that this pore region changes conformation under conditions that allow Na(+) permeation. In contrast, the latter ion conditions do not significantly affect the binding of quinidine to the pore central cavity. Based on our observations and the structural information derived from the NaK bacterial channel, we hypothesize that Ca(2+) is probably coordinated by main chain carbonyls of the pore´s first K(+)-binding site. Public Library of Science 2015-03-23 /pmc/articles/PMC4370708/ /pubmed/25798591 http://dx.doi.org/10.1371/journal.pone.0120431 Text en © 2015 Carrillo et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Carrillo, Elisa Pacheco, Lucero Balleza, Daniel Gomez-Lagunas, Froylan K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title | K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title_full | K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title_fullStr | K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title_full_unstemmed | K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title_short | K(+)-Dependent Selectivity and External Ca(2+) Block of Shab K(+) Channels |
title_sort | k(+)-dependent selectivity and external ca(2+) block of shab k(+) channels |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4370708/ https://www.ncbi.nlm.nih.gov/pubmed/25798591 http://dx.doi.org/10.1371/journal.pone.0120431 |
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