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. 1990 Oct;94(2):424–431. doi: 10.1104/pp.94.2.424

Interaction of the Depolarization-Activated K+ Channel of Samanea saman with Inorganic Ions: A Patch-Clamp Study 1,2

Nava Moran 1,2,3, David Fox 1,2,3, Ruth L Satter 1,2,3
PMCID: PMC1077249  PMID: 16667730

Abstract

A depolarization-activated K+ channel capable of carrying the large K+ currents that flow from shrinking cells during movements of Samanea saman leaflets has been described in the plasmalemma of Samanea motor cell protoplasts (N Moran et al [1988] Plant Physiol 88:643-648). We now characterize this channel in greater detail. It is selective for K+ over other monovalent ions, with the following order of relative permeability: K+ > Rb+ > Na+ ≃ Cs+ ≃ Li+. It is blocked by Cs+ and by Ba2+ in a voltage dependent manner, exhibiting a `long-pore' behavior, similarly to various types of K+ channels in animal systems. Cadmium, known for its blockage of Ca2+ channels in animal systems, and Gd3+, closely related to La3+, which also blocks Ca2+ channels in animal cells, both block K+ currents in Samanea in a voltage-independent manner, and without interfering with the kinetics of the currents. The suggested mechanism of block is either (a) by a direct interaction with the K+ channel, but external to its lumen, or, alternatively, (b) by blocking putative Ca2+ channels, and preventing the influx of Ca2+, on which the activation of the K+ channels may be dependent.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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