Glutamic Acid in the Inhibitory Site of Mitochondrial ATPase Inhibitor, IF1, Participates in pH Sensing in Both Mammals and Yeast

摘要: The mitochondrial ATPase inhibitor, IF(1), regulates the activity of F(1)F(o)-ATPase. inhibitory IF(1) is highly pH-dependent. effective inhibition by requires a low pH. Under basic conditions, its markedly declines. importance His49 in pH dependence bovine well-known. However, residue not conserved yeast IF(1). We previously showed that Glu21 required for but function homologous Glu mammalian clear. In this study, we examined requirement Glu26 (corresponding to IF(1)) regarding amino acid replacement. Three mutant proteins, E26A, H49K and double E26A/H49K, were overexpressed purified. All mutants retained their well at 8.2, although wild-type was approximately 10-fold less active 8.2 than 6.5. A covalent cross-linking study revealed both E26A formed tetramer E26A/H49K did not. These results indicate that, addition His49, participates sensing mechanism mediated different from dimer-tetramer model proposed previously.