A Ca^<2+>-and Voltage-Dependent Cl^--Sensitive Anion Channel in the Chara Plasmalemma: A Patch-Clamp Study

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The inside-out patch-clamp technique was applied to the plasmolyzed plasmalemma of internodes of Chara corallina without enzymatic treatment. We found two different types of channel activity that were Cl^--sensitive. Both types of channel were Ca^<2+>-dependent. However, the one that exhibited greater dependence on Ca^<2+> ions was the focus of our studies, and we named it the Ca^<2+>-dependent Cl^--sensitive anion channel. When the concentration of Ca^<2+> ions on the cytoplasmic side was 1.0μM, the Ca^<2+>-dependent Cl^--sensitive channel opened most frequently between approximately 80 and 100 mV At 10μM Ca^<2+>, it opened less frequently, and at 0.1 μM Ca^<2+> it scarcely opened at all. These observations indicate that the anion channel of interest is voltage-dependent over a restricted range of concentrations of Ca^<2+> ions. The dependence on Ca^<2+> and voltage of the channel can explain the behavior of the excitable Ca^<2+>-activated Cl^- channel in the Chara plasmalemma. The channel activity was blocked by several antagonists of calmodulin.
日本植物生理学会の論文