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Permeant anions contribute to voltage dependence of ClC-2 chloride channel by interacting with the protopore gate.
- Source :
-
Journal of Physiology . Jul2010, Vol. 588 Issue 14, p2545-2556. 12p. 1 Diagram, 7 Graphs. - Publication Year :
- 2010
-
Abstract
- It has been shown that the voltage ( Vm) dependence of ClC Cl− channels is conferred by interaction of the protopore gate with H+ ions. However, in this paper we present evidence which indicates that permeant Cl− ions contribute to Vm-dependent gating of the broadly distributed ClC-2 Cl− channel. The apparent open probability ( PA) of ClC-2 was enhanced either by changing the [Cl−]i from 10 to 200 mm or by keeping the [Cl−]i low (10 mm) and then raising [Cl−]o from 10 to 140 mm. Additionally, these changes in [Cl−] slowed down channel closing at positive Vm suggesting that high [Cl−] increased pore occupancy thus hindering closing of the protopore gate. The identity of the permeant anion was also important since the PA( Vm) curves were nearly identical with Cl− or Br− but shifted to negative voltages in the presence of SCN− ions. In addition, gating, closing rate and reversal potential displayed anomalous mole fraction behaviour in a SCN−/Cl− mixture in agreement with the idea that pore occupancy by different permeant anions modifies the Vm dependence ClC-2 gating. Based on the ec1-ClC anion pathway, we hypothesized that opening of the protopore gate is facilitated when Cl− ions dwell in the central binding site. In contrast, when Cl− ions dwell in the external binding site they prevent the gate from closing. Finally, this Cl−-dependent gating in ClC-2 channels is of physiological relevance since an increase in [Cl−]o enhances channel opening when the [Cl−]i is in the physiological range. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00223751
- Volume :
- 588
- Issue :
- 14
- Database :
- Academic Search Index
- Journal :
- Journal of Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 52267448
- Full Text :
- https://doi.org/10.1113/jphysiol.2010.189175