Evidence for a Multi-ion Pore Behavior in the Plant Potassium Channel KAT1

Evidence for a Multi-ion Pore Behavior in the Plant Potassium Channel KAT1 KAT1 is a cloned voltage-gated K+ channel from the plant Arabidopsis thaliana L., which displays an inward rectification reminiscent of `anomalous' rectification of the i f pacemaker current recorded in animal cells. Macroscopic conductance of KAT1 expressed in Xenopus oocytes was 5-fold less in pure Rb+ solution than in pure K+ solution, and negligible in pure Na+ solution. Experiments in different K+/Na+ or K+/Rb+ mixtures revealed deviations from the principle of independence and notably two anomalous effects of the K+/Rb+ mole fraction (i.e., the ratio [K+]/([K+]+[Rb+])). First, the KAT1 deactivation time constant was both voltage- and mole fraction-dependent (a so-called `foot in the door' effect was thus observed in KAT1 channel). Second, when plotted against the K+/Rb+ mole fraction, KAT1 conductance values passed through a minimum. This minimum is more important for two pore mutants of KAT1 (T259S and T260S) that displayed an increase in PRb/PK. These results are consistent with the idea that KAT1 conduction requires several ions to be present simultaneously within the pore. Therefore, this atypical `green' member of the Shaker superfamily of K+ channels further shows itself to be an interesting model as well for permeation as for gating mechanism studies. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Evidence for a Multi-ion Pore Behavior in the Plant Potassium Channel KAT1

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900451
Publisher site
See Article on Publisher Site

Abstract

KAT1 is a cloned voltage-gated K+ channel from the plant Arabidopsis thaliana L., which displays an inward rectification reminiscent of `anomalous' rectification of the i f pacemaker current recorded in animal cells. Macroscopic conductance of KAT1 expressed in Xenopus oocytes was 5-fold less in pure Rb+ solution than in pure K+ solution, and negligible in pure Na+ solution. Experiments in different K+/Na+ or K+/Rb+ mixtures revealed deviations from the principle of independence and notably two anomalous effects of the K+/Rb+ mole fraction (i.e., the ratio [K+]/([K+]+[Rb+])). First, the KAT1 deactivation time constant was both voltage- and mole fraction-dependent (a so-called `foot in the door' effect was thus observed in KAT1 channel). Second, when plotted against the K+/Rb+ mole fraction, KAT1 conductance values passed through a minimum. This minimum is more important for two pore mutants of KAT1 (T259S and T260S) that displayed an increase in PRb/PK. These results are consistent with the idea that KAT1 conduction requires several ions to be present simultaneously within the pore. Therefore, this atypical `green' member of the Shaker superfamily of K+ channels further shows itself to be an interesting model as well for permeation as for gating mechanism studies.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Nov 15, 1998

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