The rapid labeling of adenosine triphosphate by 32P-labeled inorganic phosphate and the exchange of phosphate oxygens as related to conformational coupling in oxidative phosphorylation

Abstract

Evidence is presented that extends and amplifies the concept that in oxidative phosphorylation energy input serves to bring about release of ATP formed at a catalytic site by reversal of hydrolysis. The evidence with beef heart submitochondrial particles includes additional demonstration of uncoupler insensitive Pi leads to HOH exhchange, demonstration that this exchange is sensitive to the specific phosphorylation inhibitor, oligomycin, and demonstration that the small burst of uncoupler-insensitive ATP, rapidly labeled after addition of a tracer of 32Pi, behaves in a manner consistent with its participation as a membrane-bound intermediate in the Pi leads to HOH exchange. In addition, data are presented showing that addition of hexokinase plus glucose to submitochondrial particles in presence of ADP and Pi considerably lowers the Pi leads to HOH exchange but that further addition of cyanide or 2,4-dinitrophenol or both has little additional effect. Such data are compatible with no energy requirement for formation of bound ATP. However, with a large excess of hexokinase, the rate of the Pi leads to HOH exchange is further depressed. This could reflect some use of energy to promote formation of ATP at the catalytic site or to maintain the integrity of the phosphorylation system. Relationships of these findings to related information in the field are discussed.