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Patch clamp analysis of the dominant plasma membrane K+ channel in root cell protoplasts of Plantago media L. Its significance for the P and K state

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Ion channels in the plasma membrane of root cell protoplasts of Plantago media L. were studied with the patch clamp technique in the cell-attached patch and outside-out patch configuration. An outward rectifying potassium channel was dominantly present in the plasma membrane. It appears responsible for the diffusional part, dominated by the K+ diffusion potential, of the cell membrane potential, in vivo. This channel is activated at potentials near to and more positive than the K+ diffusion potential. The dependence of this ion channel on K+ activity and voltage has been characterized. The current-voltage relationships of the open channel at various K+ concentrations are described by a four-state model. The membrane potential of intact protoplasts appears either dominated by the K+ diffusion potential, the protoplast is then said to be in the K state, or by the pump potential generated by the plasma membrane-bound proton pump/H+ ATPase, the P state. An experimental procedure is described to determine in cell-attached patch mode the state of the protoplast, either K or P state.

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Institution paper no.: ECOTRANS publication no. 45.

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Vogelzang, S.A., Prins, H.B.A. Patch clamp analysis of the dominant plasma membrane K+ channel in root cell protoplasts of Plantago media L. Its significance for the P and K state. J. Membarin Biol. 141, 113–122 (1994).

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Key words

  • Potassium channel
  • K state
  • P state
  • Patch clamp
  • Membrane potential
  • Root cell