Mechanism of robust circadian oscillation of KaiC phosphorylation in vitro

Abstract

By incubating the mixture of three cyanobacterial proteins, KaiA, KaiB, and KaiC, with ATP in vitro, Kondo and his colleagues reconstituted the robust circadian rhythm of the phosphorylation level of KaiC (Science, 308; 414-415 (2005)). This finding indicates that protein-protein interactions and the associated hydrolysis of ATP suffice to generate the circadian rhythm. Several theoretical models have been proposed to explain the rhythm generated in this "protein-only" system, but the clear criterion to discern different possible mechanisms was not known. In this paper, we discuss a model based on the two basic assumptions: The assumption of the allosteric transition of a KaiC hexamer and the assumption of the monomer exchange between KaiC hexamers. The model shows a stable rhythmic oscillation of the phosphorylation level of KaiC, which is robust against changes in concentration of Kai proteins. We show that this robustness gives a clue to distinguish different possible mechanisms. We also discuss the robustness of oscillation against the change in the system size. Behaviors of the system with the cellular or subcellular size should shed light on the role of the protein-protein interactions in in vivo circadian oscillation.

References in corpus (1)

• An allosteric model of KaiC phosphorylation

Cited by in corpus (4)

• Nonequilibrium thermodynamics of coupled molecular oscillators: The energy cost and optimal design for synchronization
• A Thermodynamically consistent model of the post-translational Kai circadian clock
• Computational modeling of protein interactions and phosphoform kinetics in the KaiABC cyanobacterial circadian clock
• Physical Constraints on the Rhythmicity of the Biological Clock