Effect of the natural ATPase inhibitor on the binding of adenine nucleotides and inorganic phosphate to mitochondrial F1-ATPase.
(1) Incubation of the beef heart mitochondrial ATPase, F1 with Mg-ATP was required for the binding of the natural inhibitor, IF1, to F1 to form the inactive F1-IF1 complex. When F1 was incubated in the presence of [14C]ATP and MgCl2, about 2 mol 14C-labeled adenine nucleotides were found to bind per mol of F1; the bound 14C-labeled nucleotides consisted of [14C]ADP arising from [14C]ATP hydrolysis and [14C]ATP. The 14C- labeled nucleotide binding was not prevented by IF1. These data are in agreement with the idea that the formation of the F1-IF1 complex requires an appropriate conformation of F1. (2) The 14C-labeled adenine nucleotides bound to F1 following preincubation of F1 with Mg-[14C] ATP could be exchanged with added [3H]ADP or [3H]ATP. No exchange occurred between added [3H]ADP or [3H]ATP and the 14 C-labeled adenine nucleotides bound to the F1-IF1 complex. These data suggest that the conformation of F1 in the isolated F1-IF1 complex is further modified in such a way that the bound 14C-labeled nucleotides are no longer available for exchange. (3) 32Pi was able to bind to isolated F1 with a stoichiometry of about 1 mol of Pi per mol of F1 (Penefsky, H.S. (1977) J. Biol. Chem. 252, 2891-2899). There was no binding of 32Pi to the F1-IF1 complex. Thus, not only the nucleotides sites, but also the Pi site, are masked from interaction with external ligands in the isolated F1-IF1 complex.
D000227:Adenine Nucleotides / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D004492:Edetic Acid / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D008929:Mitochondria, Heart / Q000201:enzymology*; D010086:Oxidative Phosphorylation Coupling Factors / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology*; D006180:Proton-Translocating ATPases; D000097795:ATPase Inhibitory Protein
D000227:Adenine Nucleotides; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D008274:Magnesium; D015636:Magnesium Chloride; D010086:Oxidative Phosphorylation Coupling Factors; D010710:Phosphates; D011506:Proteins; D006180:Proton-Translocating ATPases; D000097795:ATPase Inhibitory Protein