Effects of CikA and SasA co-regulation on cyanobacterial circadian clock

Abstract

Cyanobacterial circadian clock is made up of three proteins, KaiA, KaiB and KaiC. KaiA binds to the A-loop to actives the autophosphorylation of KaiC, while KaiB sequesters KaiA from the A-loop to weaken the activity of KaiA. Thus a circadian oscillator of KaiC phosphorylation generates. Recent experiments have found that CikA and SasA both play crucial roles in cyanobacterial circadian clock. They participate in the output pathway and regulate the activity of transcription factors of the core oscillator. However, the specific impact of the regulation of CikA and SasA on the system is still far from clear. To address these questions, we develop an extended mathematical model for cyanobacterial circadian clock including CikA and SasA regulation. The numerical simulation results indicate that CikA and SasA have opposite effects on the system, and the two complement each other to maintain the balance of the system. Specifically, as the concentration of SasA increases, the period and amplitude increase, and the period sensitivity to parameters, phase shift caused by dark pulses and entrainment ability are all decrease. The regulation of CikA has the opposite impact on the above aspects. Based on these results, we can adjust certain indicators of the system by adjusting the concentration of CikA or SasA. The research method in this article can provide ideas for studying the effects of other proteins on the circadian clock. The findings supplement biological studies and provide a theoretical reference for biological research. It helps us gain a deeper understanding of the dynamic mechanism of cyanobacteria circadian clock.