Sulfate is both a substrate and an activator of the voltage-dependent anion channel of Arabidopsis hypocotyl cells
1999
Frachisse, J.M. | Thomine, S. | Colcombet, J. | Guern, J. | Barbier-Brygoo, H.
On the basis of the anion content of in vitro-cultured Arabidopsis plantlets, we explored the selectivity of the voltage-dependent anion channel of the plasma membrane of hypocotyl cells. In the whole-cell configuration, substitutionof cytosolic Cl(-) by different anions led to the following sequence of relative permeabilities: NO3(-) (2.6) > or = SO4(2-) (2.0) > Cl(-) (1.0) > HCO3(-) (0.8) >> malate(2-) (0.03). Large whole-cell currents were measured for NO3(-) and SO4(2-), about five to six times higher than the equivalent Cl(-) currents. Since SO4(2-) is usually considered to be a weakly permeant or non-permeant ion, the components of the large whole-cell current were explored in more detail. Aside from its permeation through the channel with a unitary conductance, about two-thirds that of Cl(-), SO4(2-) had a regulatory effect on channel activity by preventing the run-down of the anion current both in the whole-cell and the outside-out configuration, increasing markedly the whole-cell current. The fact that the voltage-dependent plasma membrane anion channel of hypocotyl cells can mediate large NO3(-) and SO4(2-) currents and is regulated by nucleotides favors the idea that this anion channel can contribute to the cellular homeostasis of important metabolized anions.
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