Transient accumulation of elastic energy in proton translocating ATP synthase

ATP synthase is conceived as a rotatory engine with tno reversible drives, the proton-transporting membrane portion, F-0, and the catalytic peripheral portion, F-1, They are mounted on a central shaft (subunit gamma) and held together by an eccentric bearing. It is established that the hydrolysis of three molecules of ATP in F-1 drives the shaft over a full circle in three steps of 1200 each. Proton flow through F-0 probably generates a 12-steppe d rotation of the shaft so that four proton-translocating steps of 30 degre es each drive the synthesis of one molecule of ATP, We addressed the elasti city of the transmission between F-0 and F-1 in a model where the four smal ler steps in F-0 load a torsional spring which is only released under liber ation of ATP from F-1, The kinetic model of an elastic ATP synthase describ ed a wealth of published data on the synthesis/hydrolysis of ATP by F0F1 an d on proton conduction by F-0 as function of the pH and the protonmotive fo rce. The pK values of the proton-carrying group interacting with the acidic and basic sides of the membrane were estimated as 5.3-6.4 and 8.0-8.3, res pectively. (C) 1999 Federation of European Biochemical Societies.