TY - JOUR
T1 - Interaction of the depolarization-activated K+ channel of Samanea saman with inorganic ions
T2 - A patch-clamp study
AU - Moran, Nava
AU - Fox, David
AU - Satter, Ruth L.
PY - 1990/10
Y1 - 1990/10
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0001347380&partnerID=8YFLogxK
U2 - 10.1104/pp.94.2.424
DO - 10.1104/pp.94.2.424
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AN - SCOPUS:0001347380
SN - 0032-0889
VL - 94
SP - 424
EP - 431
JO - Plant Physiology
JF - Plant Physiology
IS - 2
ER -