Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium

Tikhonova LI, Pottosin II, Dietz K-J, Schönknecht G (1997)
The Plant Journal 11(5): 1059-1070.

Journal Article | Published | English

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Abstract
In contrast to the vacuolar ion channels which are gated open by an increase of cytosolic Ca2+ the vacuolar ion currents at resting cytosolic Ca2+ are poorly explored. Therefore, this study was performed to investigate the properties of the so-called fast-activating vacuolar (FV) current which dominates the electrical characteristics of the tonoplast at physiological free Ca2+ concentrations. Patch-clamp measurements were performed on whole barley (Hordeum vulgare) mesophyll vacuoles and on excised tonoplast patches. Single ion channels were identified, which, based on their selectivity, activation kinetics, Ca2+- and voltage-dependence, carry the whole-vacuole FV current. Reversal potential determinations indicated a K+ over Cl- permeability ratio of about 30. Both inward and outward whole-vacuole currents as well as the activity of single FV channels were inhibited by an increase of cytosolic Ca2+, with a Kd approximate to 6 mu M. At physiological vacuolar Ca2+ activities, the FV channel is an outward-rectifying potassium channel. The FV channel was activated in less than a few milliseconds both by negative and positive potential steps, having a minimal activity that is 40 mV negative of the K+ equilibrium potential. It is proposed that transport of K+ through this cation channel controls the electrical potential difference across the tonoplast.
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Tikhonova LI, Pottosin II, Dietz K-J, Schönknecht G. Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium. The Plant Journal. 1997;11(5):1059-1070.
Tikhonova, L. I., Pottosin, I. I., Dietz, K. - J., & Schönknecht, G. (1997). Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium. The Plant Journal, 11(5), 1059-1070.
Tikhonova, L. I., Pottosin, I. I., Dietz, K. - J., and Schönknecht, G. (1997). Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium. The Plant Journal 11, 1059-1070.
Tikhonova, L.I., et al., 1997. Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium. The Plant Journal, 11(5), p 1059-1070.
L.I. Tikhonova, et al., “Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium”, The Plant Journal, vol. 11, 1997, pp. 1059-1070.
Tikhonova, L.I., Pottosin, I.I., Dietz, K.-J., Schönknecht, G.: Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium. The Plant Journal. 11, 1059-1070 (1997).
Tikhonova, L. I., Pottosin, I. I., Dietz, Karl-Josef, and Schönknecht, G. “Fast-activating cation channel in barley mesophyll vacuoles. Inhibition by calcium”. The Plant Journal 11.5 (1997): 1059-1070.
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