Summary
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.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Beth, K. 1953. Experimentelle Untersuchungen über die Wirkung des Lichtes auf die Formbildung von kernhaltigen und kernlosenAcetabularia-Zellen.Z. Naturforsch. 8b:334–342
Cram, W.J. 1968. Compartmentation and exchange of chloride in carrot root tissue.Biochim. Biophys. Acta 163:339–353
Gradmann, D. 1975. Analog circuit of theAcetabularia membrane.J. Membrane Biol. 25:183–208
Gradmann, D. 1976. “Metabolic” action potentials inAcetabularia.J. Membrane Biol. 29:23–45
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)
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, Berlin
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 Press
Gradmann, D., Wagner, G., Gläsel, R.M. 1973. Chloride efflux during light-triggered action potentials inAcetabularia mediterranea.Biochim. Biophys. Acta 323:151–155
Hämmerling, J. 1944. Zur Lebensweise, Fortpflanzung und Entwicklung verschiedener Dasycladaceen.Arch. Protistenkd. 97:7–56
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)
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 525:252–264
Läuger, P. 1979. A channel mechanism for electrogenic ion pumps.Biochim. Biophys. Acta 552:143–161
Mummert, H. 1979. Transportmechanismen für K+, Na+ und Cl− in stationären und dynamischen Zuständen beiAcetabularia. Ph.D. Thesis. Universität of Tübingen, Germany
Mummert, H., Gradmann, D. 1976. Voltage dependent potassium fluxes and the significance of action potentials inAcetabularia.Biochim. Biophys. Acta 443:443–450
Saddler, H.D.W. 1970a. The ionic relations ofAcetabularia mediterranea.J. Exp. Bot. 21:345–359
Saddler, H.D.W. 1970b. The membrane potential ofAcetabularia mediterranea.J. Gen. Physiol. 55:802–821
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. 58:139–153
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Mummert, H., Hansen, U.P. & Gradmann, D. Current-voltage curve of electrogenic Cl− pump predicts voltage-dependent Cl− efflux inAcetabularia . J. Membrain Biol. 62, 139–148 (1981). https://doi.org/10.1007/BF01870206
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF01870206