Role of the reaction-structure coupling in temperature compensation of the KaiABC circadian rhythm

Abstract

When the mixture solution of cyanobacterial proteins, KaiA, KaiB, and KaiC, is incubated with ATP in vitro, the phosphorylation level of KaiC shows stable oscillations with the temperature-compensated circadian period. We analyzed this temperature compensation by developing a theoretical model describing the feedback relations among reactions and structural transitions in the KaiC molecule. The model showed that the reduced structural cooperativity should weaken the negative feedback coupling among reactions and structural transitions, which enlarges the oscillation amplitude and period, explaining the observed significant period extension upon single amino-acid residue substitution. We propose that an increase in thermal fluctuations similarly attenuates the reaction-structure feedback, explaining the temperature compensation in the KaiABC clock. The model suggests that the ATPase reactions in the CI domain of KaiC affect the period depending on how the reaction rates are modulated. The KaiABC clock provides a unique opportunity to analyze how the reaction-structure coupling regulates the system-level synchronized oscillations of molecules.

Artificial temperature-compensated biological clock using temperature-sensitive Belousov–Zhabotinsky gels

“…Namely, even if raising the temperature increases a reaction rate that determines the period of oscillation, another temperature-sensitive inhibitory molecule simultaneously slows the perioddetermining reaction, resulting in the balance of period [11][12][13] . There are both experimental and theoretical studies on the mechanism that utilizes chemical interactions of proteins 14,15 , temperature-amplitude coupling 16 , reaction networks with feedback loop 17 , and so on 18,19 . Focusing on chemical oscillators, including the BZ reaction, the period becomes temperature compensated when the values of activation energy suffice a certain balance equation 20 .…”