Charge displacements during ATP-hydrolysis and synthesis of the Na+-transporting FoF1-ATPase of Ilyobacter tartaricus

Transient electrical currents generated by the Na+-transporting F0F1-ATPase of IIyobacter 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 F0F1-ATPase that is related to the translocation of the cation through the membrane bound F-0 subcomplex of the ATPase. In addition, we have determined rate constants for the process: For ATP hydrolysis this reaction has a rate constant of 15-30 s(-1) if H+ is transported and 30-60 s(-1) if Na+ is transported. For ATP synthesis the rate constant is 50-70 s(-1).