The molecular mechanism of action of the proton ionophore FCCP (carbonylcyanide p-trifluoromethoxyphenylhydrazone)

Biophys J. 1983 Mar;41(3):381-98. doi: 10.1016/S0006-3495(83)84449-X.


We propose a simple model that accounts for the ability of the weak acid FCCP (Carbonylcyanide-p-trifluoromethoxyphenylhydrazone) to both transport protons across phospholipid bilayer membranes and uncouple oxidation from phosphorylation in mitochondria. Four parameters are required to characterize this model: the rate constant for the movement of A- across the membrane, kA, the rate constant for the movement of HA across the membrane, kHA, the adsorption coefficient of A- onto the membrane-solution interface, beta A, and the surface pK. These four parameters were determined from kinetic measurements on planar bilayer membranes using the charge-pulse and voltage-clamp techniques. We confirmed the adequacy of the model by determining each of these parameters independently, utilizing equilibrium dialysis, zeta potential, membrane potential, spectrophotometric, and conductance measurements. For a phosphatidylethanolamine bilayer the values of the parameters are kHA = 10(4)S-1, beta A = 3 10(-3) cm, and 6.0 less than pK less than 6.4. As predicted theoretically, the value of KA depends on both the applied voltage, V, and dielectric constant of the membrane, epsilon r; when V approaches zero and the membrane contains chlorodecane (epsilon r congruent to 2.7) kA = 700 s-1. If oxidation is coupled to phosphorylation by means of a delta microH+, and V er congruent to 2.7 for the inner membrane of the mitochondrion, the model predicts that FCCP should exert maximal uncoupling activity at a pH congruent to pK. This prediction agrees with the published experimental results.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone* / pharmacology
  • Hydrogen-Ion Concentration
  • Kinetics
  • Lipid Bilayers*
  • Mathematics
  • Membrane Potentials / drug effects
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Models, Biological
  • Nitriles* / pharmacology
  • Oxidative Phosphorylation / drug effects
  • Phosphatidylcholines
  • Phosphatidylethanolamines
  • Thermodynamics


  • Lipid Bilayers
  • Nitriles
  • Phosphatidylcholines
  • Phosphatidylethanolamines
  • 1,2-diphytanoylphosphatidylcholine
  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone