On the gating mechanism of the slowly activating vacuolar channels of Arabidopsis thaliana cultured cells

The possible involvement of intravacuolar Ca2+ and Mg2+ in the gating mecha nism of the slowly activating vacuolar (SV)-type channels was examined in i solated vacuoles of Arabidopsis thaliana (L.) Heynh. cultured cells by mean s of the patch clamp technique in the whole-vacuole configuration. Although buffering Ca2+ to submicromolar levels, independently of the Mg2+ concentr ation, increased the current amplitude and shifted the activation potential to less positive transtonoplast voltages, the time courses of activation a nd deactivation of the currents and the closure of the channels at negative transtonoplast voltages were unaffected by either of the divalent cations, suggesting that the channels are gated by voltage rather than by Ca2+ and Mg2+ and belong to the superfamily of the voltage-dependent channels.