Abstract
We recently demonstrated a self-sustainable robust circadian oscillation of KaiC phosphorylation by reconstituting KaiA, KaiB and KaiC proteins with ATP in vitro. The temperature-compensated ATPase activity of KaiC oscillates in a circadian manner in vitro. The activities of KaiC mutant variants without KaiA and KaiB were directly proportional to their cycle frequencies, indicating that the ATPase activity defines the circadian oscillation period. The mechanism of circadian clock is intrinsic to KaiC itself. The crystal structure of hexameric KaiC revealed that ATP molecules are wedged between individual KaiC subunits and that two phosphorylation sites are near the ATP binding regions. We will discuss the temperature compensation of ATPase activity and the conformational change of ATP-binding domain of KaiC.
