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Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction
Patch clamp experiments on single MaxiK channels expressed in HEK293 cells were performed at high temporal resolution (50-kHz filter) in asymmetrical solutions containing 0, 25, 50, or 150 mM Tl(+) on the luminal or cytosolic side with [K(+)] + [Tl(+)] = 150 mM and 150 mM K(+) on the other side. Out...
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Formato: | Texto |
Lenguaje: | English |
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The Rockefeller University Press
2008
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2279167/ https://www.ncbi.nlm.nih.gov/pubmed/18378799 http://dx.doi.org/10.1085/jgp.200809956 |
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author | Schroeder, Indra Hansen, Ulf-Peter |
author_facet | Schroeder, Indra Hansen, Ulf-Peter |
author_sort | Schroeder, Indra |
collection | PubMed |
description | Patch clamp experiments on single MaxiK channels expressed in HEK293 cells were performed at high temporal resolution (50-kHz filter) in asymmetrical solutions containing 0, 25, 50, or 150 mM Tl(+) on the luminal or cytosolic side with [K(+)] + [Tl(+)] = 150 mM and 150 mM K(+) on the other side. Outward current in the presence of cytosolic Tl(+) did not show fast gating behavior that was significantly different from that in the absence of Tl(+). With luminal Tl(+) and at membrane potentials more negative than −40 mV, the single-channel current showed a negative slope resistance concomitantly with a flickery block, resulting in an artificially reduced apparent single-channel current I(app). The analysis of the amplitude histograms by β distributions enabled the estimation of the true single-channel current and the determination of the rate constants of a simple two-state O-C Markov model for the gating in the bursts. The voltage dependence of the gating ratio R = I(true)/I(app) = (k(CO) + k(OC))/k(CO) could be described by exponential functions with different characteristic voltages above or below 50 mM Tl(+). The true single-channel current I(true) decreased with Tl(+) concentrations up to 50 mM and stayed constant thereafter. Different models were considered. The most likely ones related the exponential increase of the gating ratio to ion depletion at the luminal side of the selectivity filter, whereas the influence of [Tl(+)] on the characteristic voltage of these exponential functions and of the value of I(true) were determined by [Tl(+)] at the inner side of the selectivity filter or in the cavity. |
format | Text |
id | pubmed-2279167 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2008 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22791672008-10-01 Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction Schroeder, Indra Hansen, Ulf-Peter J Gen Physiol Articles Patch clamp experiments on single MaxiK channels expressed in HEK293 cells were performed at high temporal resolution (50-kHz filter) in asymmetrical solutions containing 0, 25, 50, or 150 mM Tl(+) on the luminal or cytosolic side with [K(+)] + [Tl(+)] = 150 mM and 150 mM K(+) on the other side. Outward current in the presence of cytosolic Tl(+) did not show fast gating behavior that was significantly different from that in the absence of Tl(+). With luminal Tl(+) and at membrane potentials more negative than −40 mV, the single-channel current showed a negative slope resistance concomitantly with a flickery block, resulting in an artificially reduced apparent single-channel current I(app). The analysis of the amplitude histograms by β distributions enabled the estimation of the true single-channel current and the determination of the rate constants of a simple two-state O-C Markov model for the gating in the bursts. The voltage dependence of the gating ratio R = I(true)/I(app) = (k(CO) + k(OC))/k(CO) could be described by exponential functions with different characteristic voltages above or below 50 mM Tl(+). The true single-channel current I(true) decreased with Tl(+) concentrations up to 50 mM and stayed constant thereafter. Different models were considered. The most likely ones related the exponential increase of the gating ratio to ion depletion at the luminal side of the selectivity filter, whereas the influence of [Tl(+)] on the characteristic voltage of these exponential functions and of the value of I(true) were determined by [Tl(+)] at the inner side of the selectivity filter or in the cavity. The Rockefeller University Press 2008-04 /pmc/articles/PMC2279167/ /pubmed/18378799 http://dx.doi.org/10.1085/jgp.200809956 Text en Copyright © 2008, The Rockefeller University Press 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 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Articles Schroeder, Indra Hansen, Ulf-Peter Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title | Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title_full | Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title_fullStr | Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title_full_unstemmed | Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title_short | Tl(+)-induced μs Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction |
title_sort | tl(+)-induced μs gating of current indicates instability of the maxik selectivity filter as caused by ion/pore interaction |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2279167/ https://www.ncbi.nlm.nih.gov/pubmed/18378799 http://dx.doi.org/10.1085/jgp.200809956 |
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