The Journal of Membrane Biology

, Volume 159, Issue 1, pp 83–94

Two Different Conductances Contribute to the Anion Currents in Coffea arabica Protoplasts

  • S. Dieudonné
  • M.E. Forero
  • I. Llano
Article

DOI: 10.1007/s002329900271

Cite this article as:
Dieudonné, S., Forero, M. & Llano, I. J. Membrane Biol. (1997) 159: 83. doi:10.1007/s002329900271

Abstract

The anion conductance of the plasma membrane of Coffea arabica protoplasts was isolated and characterized using the whole-cell patch clamp technique. Voltage pulse protocols revealed two components: a voltage-gated conductance (Gs) and a voltage-independent one (Gl). Gs is activated upon depolarization (e-fold activation every +36 mV) with time constants of 1 sec and 5 sec at all potentials. Gl and Gs also differ by their kinetic and biophysical properties. In bi-ionic conditions the current associated with Gs shows strong outward rectification and its permeability sequence is F > NO3 > Cl. In the same conditions the current associated with Gl does not rectify and its permeability sequence is F≫ NO3= Cl. Furthermore, at potentials over +50 mV Gs, but not Gl, increases with a time constant of several minutes. Finally the gating of Gs is affected by stretch of the membrane, which leads to an increased activation and a reduced voltage sensitivity. Anion conductances similar to the ones described here have been found in many plant preparations but Gl-type components have been generally interpreted as the background activation of the slow voltage-gated channels (corresponding to Gs). We show that in coffee protoplasts Gl and Gs are kinetically and biophysically distinct, suggesting that they correspond to two different molecular entities.

Key words: Anion channels — Plants — Ionic selectivity — Voltage-dependence — Stretch — Patch clamp

Copyright information

© Springer-Verlag New York Inc. 1997

Authors and Affiliations

  • S. Dieudonné
    • 1
  • M.E. Forero
    • 1
  • I. Llano
    • 1
  1. 1.Laboratorio de Biofísica, Laboratorio de Biofísica, Centro Internacional de Física, Edificio Manuel AncizarCiudad UniversitariaBogotáColombia