Structural and functional modifications induced by diamide on the F 0sector of the mammalian ATP synthase

In this report data are presented which firmly establish that by treating isolated F 0with the thiol reagent diamide, two 25 kDa F 0subunits react to form a dimer of 45 kDa apparent molecular mass. This dimerising effect is correlated to the impairment of the binding of F 1to F 0, both at μM and mM diamide concentrations. Under the latter condition, modification of other F 0subunits also occurs. Passive proton conductance through F 0, as well as its sensitivity to N, N′-dicyclohexylcarbodiimide, are affected at low diamide concentration. Thus perturbation of the cysteine residue of the 25 kDd F 0subunit is sufficient for altering the ATP synthase proton channel.