Structural basis of unisite catalysis of bacterial F0F1-ATPase.

ABSTRACT

Adenosine triphosphate (ATP) synthases (F0F1-ATPases) are crucial for all aerobic organisms. F1, a water-soluble domain, can catalyze both the synthesis and hydrolysis of ATP with the rotation of the central γε rotor inside a cylinder made of α 3 ß 3 in three different conformations (referred to as ß E, ß TP, and ß DP). In this study, we determined multiple cryo-electron microscopy structures of bacterial F0F1 exposed to different reaction conditions. The structures of nucleotide-depleted F0F1 indicate that the ε subunit directly forces ß TP to adopt a closed form independent of the nucleotide binding to ß TP. The structure of F0F1 under conditions that permit only a single catalytic ß subunit per enzyme to bind ATP is referred to as unisite catalysis and reveals that ATP hydrolysis unexpectedly occurs on ß TP instead of ß DP, where ATP hydrolysis proceeds in the steady-state catalysis of F0F1. This indicates that the unisite catalysis of bacterial F0F1 significantly differs from the kinetics of steady-state turnover with continuous rotation of the shaft.