ATP synthase inhibitor prevents the enzyme from switching to ATP hydrolysis during collapse of the electrochemical gradient, for example during oxygen deprivation [1] ATP synthase inhibitor forms a one to one complex with the F1 ATPase, possibly by binding at the alpha-beta interface. It is thought to inhibit ATP synthesis by preventing the release of ATP [2]. The minimum inhibitory region for bovine inhibitor (Swiss:P01096) is from residues 39 to 72 [2]. The inhibitor has two oligomeric states, dimer (the active state) and tetramer. At low pH , the inhibitor forms a dimer via antiparallel coiled coil interactions between the C terminal regions of two monomers. At high pH, the inhibitor forms tetramers and higher oligomers by coiled coil interactions involving the N terminus and inhibitory region, thus preventing the inhibitory activity [1].

1: Homologous and heterologous inhibitory effects of ATPase inhibitor proteins on F-ATPases. Cabezon E, Butler PJ, Runswick MJ, Carbajo RJ, Walker JE; J Biol Chem 2002;277:41334-41341. PMID:12186878

2: The ATPase inhibitor protein from bovine heart mitochondria: the minimal inhibitory sequence. van Raaij MJ, Orriss GL, Montgomery MG, Runswick MJ, Fearnley IM, Skehel JM, Walker JE; Biochemistry 1996;35:15618-15625. PMID:8961923