Structural dynamics in F1ATPase during the first reaction cycle of ATP hydrolysis

The velocity of ATP hydrolysis, catalyzed by purified F1ATPase from Micrococcus luteus, was decelerated on decreasing the temperature. At 13 degrees C one reaction cycle is completed after 20 s. Hydrolysis was triggered upon rapid mixing of the enzyme with ATP. During the first reaction cycle, succeeding structural alterations of the F1ATPase were traced by time resolved X-ray scattering. The scattering spectra obtained from consecutive intervals of 1 s, revealed the F1ATPase to pass a conformational state exhibiting an expanded (6%) molecular shape. The expanded state was observed between 45% and 65% of the time required to complete the reaction cycle. This points out a conformational pulsation during ATP hydrolysis.