Mutations in the K+-Channel KcsA Toward Kir Channels Alter Salt-Induced Clusterization and Blockade by Quaternary Alkylammonium Ions

Mutations in the K+-Channel KcsA Toward Kir Channels Alter Salt-Induced Clusterization and... Protein aggregation is a result of malfunction in protein folding, assembly, and transport, caused by protein mutation and/or changes in the cell environment, thus triggering many human diseases. We have shown that bacterial K+-channel KcsA, which acts as a representative model for ion channels, forms salt-induced large conductive complexes in a particular environment. In the present study, we investigated the effects of point mutations in the selectivity filter of KcsA on intrinsic stability, aggregation, and channel blocking behavior. First, we found that a low sodium chloride concentration in potassium-containing media induced fast transfer of single channels to a planar lipid bilayer. Second, increasing the sodium chloride concentration drastically increased the total channel current, indicating enhanced vesicle fusion and transfer of multiple channels to a planar lipid bilayer. However, such complexes exhibited high conductance as well as higher open probability compared to the unmodified KcsA behavior shown previously. Interestingly, the affinity of aggregated complexes for larger symmetric quaternary alkylammonium ions (QAs) was found to be much higher than that for tetraethylammonium, a classical blocker of the K+ channel. Based on these findings, we propose that mutant channel complexes exhibit larger pore dimensions, thus resembling more the topological properties of voltage-gated and inwardly rectifying K+ channels. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Mutations in the K+-Channel KcsA Toward Kir Channels Alter Salt-Induced Clusterization and Blockade by Quaternary Alkylammonium Ions

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Publisher
Springer-Verlag
Copyright
Copyright © 2009 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-009-9223-z
Publisher site
See Article on Publisher Site

Abstract

Protein aggregation is a result of malfunction in protein folding, assembly, and transport, caused by protein mutation and/or changes in the cell environment, thus triggering many human diseases. We have shown that bacterial K+-channel KcsA, which acts as a representative model for ion channels, forms salt-induced large conductive complexes in a particular environment. In the present study, we investigated the effects of point mutations in the selectivity filter of KcsA on intrinsic stability, aggregation, and channel blocking behavior. First, we found that a low sodium chloride concentration in potassium-containing media induced fast transfer of single channels to a planar lipid bilayer. Second, increasing the sodium chloride concentration drastically increased the total channel current, indicating enhanced vesicle fusion and transfer of multiple channels to a planar lipid bilayer. However, such complexes exhibited high conductance as well as higher open probability compared to the unmodified KcsA behavior shown previously. Interestingly, the affinity of aggregated complexes for larger symmetric quaternary alkylammonium ions (QAs) was found to be much higher than that for tetraethylammonium, a classical blocker of the K+ channel. Based on these findings, we propose that mutant channel complexes exhibit larger pore dimensions, thus resembling more the topological properties of voltage-gated and inwardly rectifying K+ channels.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Dec 27, 2009

References

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