Blockade of potassium channels in the plasmalemma of Chara corallina by tetraethylammonium, Ba2+, Na+ and Cs+

Mark Tester*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

The outer membranes of plant cells contain channels which are highly selective for K+. In the giant-celled green alga Chara corallina, K+ currents in the plasmalemma were measured during the action potential and when the cell was depolarized to the K+ equilibrium potential in high external K+ concentrations. Currents in both conditions were reduced by externally added tetraethylammonium (TEA+), Ba2+, Na+ and Cs+. In contrast to inhibition by TEA+, the latter three ions inhibited inward K+ current in a voltage-dependent manner, and reduced inward current more than outward. Ba2+ and Na+ also appeared to inhibit outward current in a strongly voltage-dependent manner. The blockade by Cs+ is studied in more detail in the following paper. TEA+ inhibited both inward and outward currents in a largely voltage-independent manner, with an apparent KD of about 0.7 to 1.1 mm, increasing with increasing external K+. All inhibitors reduced current towards a similar linear leak, suggesting an insensitivity of the background leak in Chara to these various K+ channel inhibitors. The selectivity of the channel to various monovalent cations varied depending on the method of measurement, suggesting that ion movement through the K+-selective channel may not be independent.

Original languageEnglish (US)
Pages (from-to)77-85
Number of pages9
JournalThe Journal of Membrane Biology
Volume105
Issue number1
DOIs
StatePublished - Oct 1988
Externally publishedYes

Keywords

  • action potential
  • current-voltage curves
  • ion channel
  • K
  • voltage clamp

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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