Abstract
The catalytic F1 complex of ATP synthase is the smallest mechanical motor known. The ATPase function is coupled to the stepwise rotation of the γ subunit in a catalytic core formed by three copies of subunits α and β. Tentoxin, a cyclic peptide produced by phytopathogenic fungi of the Alternaria species inactivates the F1-ATPase in sensitive species at micromolar concentrations, whereas milimolar amounts of the toxin restore and surpass the natural enzyme activity. Although it is known that this inhibition and stimulation is related to the binding of one and two or three molecules of tentoxin, the mechanism of the change of the activity is not known very well. Here we report the detailed molecular mechanism of the regulation revealed by the single molecule analysis.
