Cooperativity between the enzymatic sites of F-1-ATPase revisited by the use of HPLC methods

The fundamental question of the cooperativity between the enzymatic sites o f F-1-ATPase is examined in the light of new measurements of the enzymatic rate of ATP hydrolysis by CF1, the enzyme isolated from spinach chloroplast s. The experimental data, obtained with a chromatographic method, fit a mod el that involves two kinds of independent enzymatic sites working with meta l-free ATP, with no need of cooperativity between the sites. Binding measur ements between ADP or ATP and CF1 by the chromatographic method of Hummel a nd Dreyer (1962) also support this conclusion. The present data and interpr etation are in agreement with those reported recently (Reynafarje and Peder sen, 1996) which show that the first order rate constant of ATP hydrolysis by MF1, the analogous enzyme from mitochondria, is virtually constant under experimental conditions involving either unisite or multisite hydrolysis o f ATP. The present data and interpretation are discussed together with thos e reported previously, in particular with regard to the methods that were u sed to support the commonly accepted opposite viewpoint.