Kinetic equivalence of transmembrane pH and electrical potential differences in ATP synthesis

J Biol Chem. 2012 Mar 16;287(12):9633-9. doi: 10.1074/jbc.M111.335356. Epub 2012 Jan 17.


ATP synthase is the key player of Mitchell's chemiosmotic theory, converting the energy of transmembrane proton flow into the high energy bond between ADP and phosphate. The proton motive force that drives this reaction consists of two components, the pH difference (ΔpH) across the membrane and transmembrane electrical potential (Δψ). The two are considered thermodynamically equivalent, but kinetic equivalence in the actual ATP synthesis is not warranted, and previous experimental results vary. Here, we show that with the thermophilic Bacillus PS3 ATP synthase that lacks an inhibitory domain of the ε subunit, ΔpH imposed by acid-base transition and Δψ produced by valinomycin-mediated K(+) diffusion potential contribute equally to the rate of ATP synthesis within the experimental range examined (ΔpH -0.3 to 2.2, Δψ -30 to 140 mV, pH around the catalytic domain 8.0). Either ΔpH or Δψ alone can drive synthesis, even when the other slightly opposes. Δψ was estimated from the Nernst equation, which appeared valid down to 1 mm K(+) inside the proteoliposomes, due to careful removal of K(+) from the lipid.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / biosynthesis*
  • Adenosine Triphosphate / chemistry*
  • Bacillus / chemistry
  • Bacillus / enzymology
  • Bacillus / physiology*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Electricity
  • Hydrogen-Ion Concentration
  • Kinetics
  • Membrane Potentials
  • Proton-Translocating ATPases / chemistry
  • Proton-Translocating ATPases / genetics
  • Proton-Translocating ATPases / metabolism


  • Bacterial Proteins
  • Adenosine Triphosphate
  • Proton-Translocating ATPases