ATPase inhibitor, mitochondrial is an enzyme that in humans is encoded by the ATPIF1gene.
This gene encodes a mitochondrial ATPase inhibitor. Alternative splicing occurs at this locus and three transcript variants encoding distinct isoforms have been identified.
It prevents ATPase from switching to ATPhydrolysis during collapse of the electrochemical gradient, for example during oxygen deprivation  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. The inhibitor has two oligomeric states, dimer (the active state) and tetramer. At low pH, the inhibitor forms a dimer via antiparallelcoiled 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.
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