The Journal of Membrane Biology

, Volume 37, Issue 1, pp 361–396

The kinetic mechanism of action of an uncoupler of oxidative phosphorylation

  • Fredric S. Cohen
  • Moisés Eisenberg
  • Stuart McLaughlin
Article

DOI: 10.1007/BF01940940

Cite this article as:
Cohen, F.S., Eisenberg, M. & McLaughlin, S. J. Membrain Biol. (1977) 37: 361. doi:10.1007/BF01940940

Summary

The chemiosmotic hypothesis predicts that the mechanism by which weak acids uncouple oxidative phosphorylation in mitochondria is identical to the mechanism by which they transport hydrogen ions across artificial bilayer membranes. We report here the results of a kinetic study of uncoupler-mediated hydrogen ion transport across bilayer membranes. We made electrical relaxation measurements on black lipid membranes exposed to the substituted benzimidazole 5,6-dichloro-2-trifluoromethylbenzimidazole. The simplest model consistent with our experimental data allowed us to deduce values for adsorption coefficients and rate constants. Our major conclusions are that the back diffusion of the neutral species is the rate limiting step for the steady state transport of hydrogen ions, that both the neutral and charged forms of the uncoupler adsorb strongly to the interfaces, and that the reactions at the membrane-solution interfaces occur sufficiently rapidly for equilibrium to be maintained. Independent measurements of the adsorption coefficients of both the neutral and anionic forms of the weak acid and also of the permeability of the membrane to the neutral form agreed well with the values deduced from the kinetic study.

Copyright information

© Springer-Verlag New York Inc 1977

Authors and Affiliations

  • Fredric S. Cohen
    • 1
  • Moisés Eisenberg
    • 1
  • Stuart McLaughlin
    • 1
  1. 1.Health Sciences CenterS.U.N.Y.Stony Brook
  2. 2.Department of PhysiologyA. Einstein College of MedicineBronx