The nucleotide binding site of F1-ATPase which carries out uni-site catalysis is one of the alternating active sites of the enzyme

Nucleotide-depleted mitochondrial F1-ATPase binds 3'-(2')-O-(2-nitro-4-azidobenzoyl)-derivatives of ATP (NAB-ATP) and GTP (NAB-GTP) when these nucleotide analogues are added to the enzyme in equimolar quantities in the presence of Mg2+ (uni-site catalysis conditions). The binding of NAB-ATP is accompanied by its hydrolysis and inorganic phosphate dissociation from the enzyme; NAB-ADP remains bound to F1-ATPase. The F1-ATPase X NAB-ADP complex has no ATPase activity and its reactivation in the presence of an excess of ATP is accompanied by NAB-ADP release. The illumination of the F1-ATPase complexes with NAB-ADP or NAB-GDP leads to the covalent binding of one nucleotide analogue molecule to the enzyme and to the irreversible inactivation of F1-ATPase. It follows from the results obtained that the modification of just one of the F1-ATPase catalytic sites is sufficient to complete the inhibition of ATPase activity.