Skip to main content
PMC home page
Plant Physiology logoLink to Plant Physiology
. 1982 Apr;69(4):781–788. doi: 10.1104/pp.69.4.781

Potassium Channels in Chara corallina1

CONTROL AND INTERACTION WITH THE ELECTROGENIC H+ PUMP

David W Keifer 1, William J Lucas 1
PMCID: PMC426305  PMID: 16662296

Abstract

Plasmalemma electrical properties were used to investigate K+ transport and its control in internodal cells of Chara corallina Klein ex Willd., em R.D.W. Cell exposure to solutions containing 10 mm KCl caused the potential, normally −250 millivolts (average), to depolarize in two steps. The first step was a 21 millivolt depolarization that lasted from 1 to 40 minutes. The second step started with an action potential and left the membrane potential at −91 millivolts, with a 10-fold reduction in resistance. We suggest that the second step was caused by the opening of K+ -channels in the membrane. This lowered the resistance and provided a current pathway that partially short-circuited the electrogenic pump. Although largely short-circuited, the electrogenic pump was still operating as indicated by: (a) the depolarized potential of −91 millivolts was more negative than Ek (=−42 millivolts in 10 mm K+); (b) a large net K+ uptake occurred while the cell was depolarized; (c) both the electrogenic pump inhibitor, diethylstilbestrol, and the sulfhydryl-reagent N-ethylmaleimide (which increased the passive membrane permeability) further depolarized the potential in 10 mm KCl.

A two-phase recovery back to normal cell potentials occurred upon lowering the K+ concentration from 10 to 0.2 mm. The first phase was an apparent Nernst potential response to the change in external K+ concentration. The second phase was a sudden hyperpolarization accompanied by a large increase in membrane resistance. We attribute the second phase to the closing of K+ -channels and the removal of the associated short-circuiting effect on the electrogenic pump, thereby allowing the membrane to hyperpolarize. Further experiments indicated that the K+ -channel required Ca2+ for normal closure, but other ions could substitute, including: Na+, tetraethylammonium, and 2,4,6-triaminopyrimidine. Apparently, K+ -channel conductance is determined by competition between Ca2+ and K+ for a control (gating?) binding site.

Full text

PDF
781

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Findlay G. P., Hope A. B., Pitman M. G., Smith F. A., Walker N. A. Ionic fluxes in cells of Chara corallina. Biochim Biophys Acta. 1969;183(3):565–576. doi: 10.1016/0005-2736(69)90170-9. [DOI] [PubMed] [Google Scholar]
  2. Hille B. Potassium channels in myelinated nerve. Selective permeability to small cations. J Gen Physiol. 1973 Jun;61(6):669–686. doi: 10.1085/jgp.61.6.669. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Hogg J., Williams E. J., Johnston R. J. A simplified method for measuring membrane resistances in Nitella translucens. Biochim Biophys Acta. 1968 Apr 29;150(3):518–520. doi: 10.1016/0005-2736(68)90152-1. [DOI] [PubMed] [Google Scholar]
  4. Keifer D. W., Spanswick R. M. Activity of the Electrogenic Pump in Chara corallina as Inferred from Measurements of the Membrane Potential, Conductance, and Potassium Permeability. Plant Physiol. 1978 Oct;62(4):653–661. doi: 10.1104/pp.62.4.653. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Keifer D. W., Spanswick R. M. Correlation of Adenosine Triphosphate Levels in Chara corallina with the Activity of the Electrogenic Pump. Plant Physiol. 1979 Aug;64(2):165–168. doi: 10.1104/pp.64.2.165. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Lichtner F. T., Lucas W. J., Spanswick R. M. Effect of Sulfhydryl Reagents on the Biophysical Properties of the Plasmalemma of Chara corallina. Plant Physiol. 1981 Oct;68(4):899–904. doi: 10.1104/pp.68.4.899. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Lucas W. J., Dainty J. HCO(3) Influx Across the Plasmalemma of Chara corallina: Divalent Cation Requirement. Plant Physiol. 1977 Dec;60(6):862–867. doi: 10.1104/pp.60.6.862. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Lucas W. J. HCO(3) Influx across the Plasmalemma of Chara corallina: Physiological and Biophysical Influence of 10 mm K. Plant Physiol. 1978 Apr;61(4):487–493. doi: 10.1104/pp.61.4.487. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Reuss L., Grady T. P. Triaminopyrimidinium (TAP+) blocks luminal membrane K conductance in Necturus gallbladder epithelium. J Membr Biol. 1979 Jul 31;48(3):285–298. doi: 10.1007/BF01872896. [DOI] [PubMed] [Google Scholar]
  10. Spanswick R. M. Evidence for an electrogenic ion pump in Nitella translucens. I. The effects of pH, K + , Na + , light and temperature on the membrane potential and resistance. Biochim Biophys Acta. 1972 Oct 23;288(1):73–89. doi: 10.1016/0005-2736(72)90224-6. [DOI] [PubMed] [Google Scholar]
  11. TASAKI I., HAGIWAR A. S. Demonstration of two stable potential states in the squid giant axon under tetraethylammonium chloride. J Gen Physiol. 1957 Jul 20;40(6):859–885. doi: 10.1085/jgp.40.6.859. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. TOBIAS J. M. A CHEMICALLY SPECIFIED MOLECULAR MECHANISM UNDERLYING EXCITATION IN NERVE: A HYPOTHESIS. Nature. 1964 Jul 4;203:13–17. doi: 10.1038/203013a0. [DOI] [PubMed] [Google Scholar]
  13. Thompson S. H. Three pharmacologically distinct potassium channels in molluscan neurones. J Physiol. 1977 Feb;265(2):465–488. doi: 10.1113/jphysiol.1977.sp011725. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Physiology are provided here courtesy of Oxford University Press

RESOURCES