Calmodulin regulates the Ca2+-dependent slow-vacuolar ion channel in the tonoplast of Chenopodium rubrum suspension cells |
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Authors: | Thomas Weiser Wilfried Blum Friedrich-Wilhelm Bentrup |
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Institution: | (1) Botanisches Institut I der Justus-Liebig-Universität, Senckenbergstrasse 17-21, W-6300 Giessen, Germany |
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Abstract: | The patch-clamp technique was applied to vacuoles isolated from a photoautotrophic suspension cell culture of Chenopodium rubrum L. and vacuolar clamp currents, which are predominantly carried by the previously identified Ca2+-dependent slow vacuolar (SV) ion channels, were recorded. These currents, which were activated by 1-s voltage pulses of -100 mV (vacuolar interior negative) in the presence of 100 M Ca2+ (cytosolic side), could be blocked completely and reversibly by the calmodulin antagonist W-7 N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide] and its chlorine-deficient analogue W-5; half-maximum inhibition was found at approx. 6 M for W-7 and 70 M for W-5. Inhibition was reversed by addition of 1 g · ml–1 calmodulin purified from Chenopodium cell suspensions; reversal by bovine brain calmodulin was scarcely appreciable. We conclude that cytosolic calmodulin mediates the Ca2+ dependence of the SV-channel in the Chenopodium tonoplast.Abbreviations SV-channel
slowly activated, vacuolar ion channel
- W-5
N-(6-aminohexyl)-1-naphthalenesulfonamide
- W-7
N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide
We acknowledge support by the Deutsche Forschungsgemeinschaft and the Bundesminister für Forschung und Technologie, Bonn, and by the Justus-Liebig-Universität Giessen (to W.B.) |
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Keywords: | Calmodulin Chenopodium Ion channel (slow vacuolar) Suspension cell culture Tonoplast |
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