The noncatalytic site‐deficient α3β3γ subcomplex and FoF1‐ATP synthase can continuously catalyse ATP hydrolysis when Pi is present

We investigated ATP hydrolysis by a mutant (ΔNC) α3β3γ subcomplex of F0F1-ATP synthase from the thermophilic Bacillus PS3 that is defective in the noncatalytic nucleotide binding sites. This mutant subcomplex was activated by inorganic phosphate ions (Pi) and did not show continuous ATP hydrolysis activity in the absence of Pi. Pi also activated the wild-type α3β3γ subcomplex in a similar manner. Sulphate activated wild-type α3β3γ but not ΔNC α3β3γ, indicating that Pi activation did not involve noncatalytic sites but that sulphate activation did. Pi also activated ATP hydrolysis and coupled proton translocation by the wild-type and ΔNC F0F1-ATP synthases reconstituted into vesicle membranes.