Charge Displacements during ATP-Hydrolysis and Synthesis of the Na+-Transporting FoF1-ATPase of Ilyobacter tartaricus

Transient electrical currents generated by the Na+-transporting FoF1-ATPase of Ilyobacter tartaricus were observed in the hydrolytic and synthetic mode of the enzyme. Two techniques were applied: a photochemical ATP concentration jump on a planar lipid membrane and a rapid solution exchange on a solid supported membrane. We have identified an electrogenic reaction in the reaction cycle of the FoF1-ATPase that is related to the translocation of the cation through the membrane bound Fo subcomplex of the ATPase. In addition, we have determined rate constants for the process: For ATP hydrolysis this reaction has a rate constant of 15–30s−1 if H+ is transported and 30–60s−1 if Na+ is transported. For ATP synthesis the rate constant is 50–70s−1.