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Site-specific ion occupation in the selectivity filter causes voltage-dependent gating in a viral K+ channel.

Rauh, O. and Hansen, U. P. and Scheub, D. D. and Thiel, Gerhard and Schroeder, Indra (2018):
Site-specific ion occupation in the selectivity filter causes voltage-dependent gating in a viral K+ channel.
In: Scientific reports, 8 (1), p. 10406. ISSN 2045-2322,
[Article]

Abstract

Many potassium channels show voltage-dependent gating without a dedicated voltage sensor domain. This is not fully understood yet, but often explained by voltage-induced changes of ion occupation in the five distinct K binding sites in the selectivity filter. To better understand this mechanism of filter gating we measured the single-channel current and the rate constant of sub-millisecond channel closure of the viral K channel Kcv for a wide range of voltages and symmetric and asymmetric K concentrations in planar lipid membranes. A model-based analysis employed a global fit of all experimental data, i.e., using a common set of parameters for current and channel closure under all conditions. Three different established models of ion permeation and various relationships between ion occupation and gating were tested. Only one of the models described the data adequately. It revealed that the most extracellular binding site (S0) in the selectivity filter functions as the voltage sensor for the rate constant of channel closure. The ion occupation outside of S0 modulates its dependence on K concentration. The analysis uncovers an important role of changes in protein flexibility in mediating the effect from the sensor to the gate.

Item Type: Article
Erschienen: 2018
Creators: Rauh, O. and Hansen, U. P. and Scheub, D. D. and Thiel, Gerhard and Schroeder, Indra
Title: Site-specific ion occupation in the selectivity filter causes voltage-dependent gating in a viral K+ channel.
Language: English
Abstract:

Many potassium channels show voltage-dependent gating without a dedicated voltage sensor domain. This is not fully understood yet, but often explained by voltage-induced changes of ion occupation in the five distinct K binding sites in the selectivity filter. To better understand this mechanism of filter gating we measured the single-channel current and the rate constant of sub-millisecond channel closure of the viral K channel Kcv for a wide range of voltages and symmetric and asymmetric K concentrations in planar lipid membranes. A model-based analysis employed a global fit of all experimental data, i.e., using a common set of parameters for current and channel closure under all conditions. Three different established models of ion permeation and various relationships between ion occupation and gating were tested. Only one of the models described the data adequately. It revealed that the most extracellular binding site (S0) in the selectivity filter functions as the voltage sensor for the rate constant of channel closure. The ion occupation outside of S0 modulates its dependence on K concentration. The analysis uncovers an important role of changes in protein flexibility in mediating the effect from the sensor to the gate.

Journal or Publication Title: Scientific reports
Journal volume: 8
Number: 1
Divisions: 10 Department of Biology
10 Department of Biology > Plant Membrane Biophysics
Date Deposited: 17 Jul 2018 08:40
Identification Number: pmid:29991721
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