The Journal of Membrane Biology

, Volume 62, Issue 1–2, pp 139–148 | Cite as

Current-voltage curve of electrogenic Cl pump predicts voltage-dependent Cl efflux inAcetabularia

  • H. Mummert
  • U. P. Hansen
  • D. Gradmann


The current-voltage relationship of carrier-mediated, passive and active ion transport systems with one charge-carrying pathway can exactly be described by a simple reaction kinetic model. This model consists of two carrier states (one inside, one outside) and two pairs (forwards and backwards) of rate constants: a voltage-dependent one, describing the transport of charge and a voltage-insensitive one, summarizing all the other (voltage-independent) reactions. For the electrogenic Cl pump inAcetabularia these four rate constants have been determined from electrical measurements of the current-voltage relationship of the pump (Gradmann, Hansen & Slayman, 1981;in: Electrogenic Ion Pumps, Academic Press, New York). The unidirectional Cl efflux through the pump can also be calculated by the availiable reaction kinetic parameters.36Cl efflux experiments on singleAcetabularia cells with simultaneous electrical stimulation (action potentials) and recording, demonstrate the unidirectional Cl efflux to depend on the membrane potential. After subtraction of an efflux portion which bypasses the pump, agreement is found between the measured flux-voltage relationship and the theoretical one as obtained from the reaction kinetic model and its parameters from the electrical data.

Key words

Acetabularia Cl flux current-voltage relationships electrogenic pump ion-transport model nonlinear kinetics 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Beth, K. 1953. Experimentelle Untersuchungen über die Wirkung des Lichtes auf die Formbildung von kernhaltigen und kernlosenAcetabularia-Zellen.Z. Naturforsch. 8b:334–342Google Scholar
  2. 2.
    Cram, W.J. 1968. Compartmentation and exchange of chloride in carrot root tissue.Biochim. Biophys. Acta 163:339–353Google Scholar
  3. 3.
    Gradmann, D. 1975. Analog circuit of theAcetabularia membrane.J. Membrane Biol. 25:183–208Google Scholar
  4. 4.
    Gradmann, D. 1976. “Metabolic” action potentials inAcetabularia.J. Membrane Biol. 29:23–45Google Scholar
  5. 5.
    Gradmann, D., Hansen, U.-P., Slayman, C.L. 1981. Reaction kinetic analysis of current-voltage relationships for electrogenic pumps inNeurospora andAcetabularia.In: Electrogenic Ion Pumps. C.L. Slayman, editor.In: Current Topics in Membranes and Transport. F. Bronner and A. Kleinzeller, editors. Academic Press, New York (in press)Google Scholar
  6. 6.
    Gradmann, D., Klemke, W. 1974. Current-voltage relationship of the electrogenic pump inAcetabularia.In: Membrane Transport in Plants. U. Zimmermann and J. Dainty, editors. pp. 131–138. Springer-Verlag, BerlinGoogle Scholar
  7. 7.
    Gradmann, D., Mummert, H. 1980. Plant action potentials.In: Plant Membrane Transport: Current Conceptual Issues. R.M. Spanswick, W.J. Lucas, and J. Dainty, editors. pp. 333–344. Elsevier/North-Holland Biomedical PressGoogle Scholar
  8. 8.
    Gradmann, D., Wagner, G., Gläsel, R.M. 1973. Chloride efflux during light-triggered action potentials inAcetabularia mediterranea.Biochim. Biophys. Acta 323:151–155Google Scholar
  9. 9.
    Hämmerling, J. 1944. Zur Lebensweise, Fortpflanzung und Entwicklung verschiedener Dasycladaceen.Arch. Protistenkd. 97:7–56Google Scholar
  10. 10.
    Hansen, U.-P., Gradmann, D., Sanders, D., Slayman, C.L. 1981. Interpretation of current-voltage relationships for “active” transport systems. I. Steady-state reaction-kinetic analysis of Class-I mechanisms.J. Membrane Biol. (in press) Google Scholar
  11. 11.
    Karlish, S.J.D., Yates, D.W., Glynn, I.M. 1978. Conformational transitions between Na+-bound and K+-bound forms of (Na++K+)-ATPase, studied with formycin nucleotides.Biochim. Biophys. Acta 525:252–264Google Scholar
  12. 12.
    Läuger, P. 1979. A channel mechanism for electrogenic ion pumps.Biochim. Biophys. Acta 552:143–161Google Scholar
  13. 13.
    Mummert, H. 1979. Transportmechanismen für K+, Na+ und Cl in stationären und dynamischen Zuständen beiAcetabularia. Ph.D. Thesis. Universität of Tübingen, GermanyGoogle Scholar
  14. 14.
    Mummert, H., Gradmann, D. 1976. Voltage dependent potassium fluxes and the significance of action potentials inAcetabularia.Biochim. Biophys. Acta 443:443–450Google Scholar
  15. 15.
    Saddler, H.D.W. 1970a. The ionic relations ofAcetabularia mediterranea.J. Exp. Bot. 21:345–359Google Scholar
  16. 16.
    Saddler, H.D.W. 1970b. The membrane potential ofAcetabularia mediterranea.J. Gen. Physiol. 55:802–821Google Scholar
  17. 17.
    Sanders, D., Hansen, U.-P. 1981. Mechanism of Cl transport at the plasma membrane ofChara corallina II. Transinhibition and the determination of H+/Cl binding order from a reaction kinetic model.J. Membrane Biol. 58:139–153Google Scholar

Copyright information

© Springer-Verlag New York Inc 1981

Authors and Affiliations

  • H. Mummert
    • 1
  • U. P. Hansen
    • 1
  • D. Gradmann
    • 1
  1. 1.Institut für Biologie ITübingenWest Germany

Personalised recommendations