Dimerization of bovine F1-ATPase by binding the inhibitor protein, IF1.
In mitochondria, the hydrolytic activity of ATP synthase is regulated by a natural inhibitor protein, IF(1). The binding of IF(1) to ATP synthase depends on pH values, and below neutrality, IF(1) forms a stable complex with the enzyme. Bovine IF(1) has two oligomeric states, dimer and tetramer, depending on pH values. At pH 6.5, where it is active, IF(1) dimerizes by formation of an antiparallel alpha-helical coiled-coil in its C-terminal region. This arrangement places the inhibitory N-terminal regions in opposition, implying that active dimeric IF(1) can bind two F(1) domains simultaneously. Evidence of dimerization of F(1)-ATPase by binding to IF(1) is provided by gel filtration chromatography, analytical ultracentrifugation, and electron microscopy. At present, it is not known whether IF(1) can bring about the dimerization of the F(1)F(0)-ATPase complex.
Medical Research Council Dunn Human Nutrition Unit, Cambridge CB2 2XY and The Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom.
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D000818:Animals; D002417:Cattle; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000737:chemistry*; D008854:Microscopy, Electron; D008970:Molecular Weight; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000737:chemistry*
D004791:Enzyme Inhibitors; D006180:Proton-Translocating ATPases