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Circadian KaiC phosphorylation: a multi-layer network.
Congxin Li1, Xiaofang Chen, Pengye Wang
1Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
Plos Computational Biology
|November 26, 2009
Summary
Cyanobacteria's circadian clock relies on KaiC phosphorylation. Diverse KaiC forms create complex rhythms, with specific sites regulating oscillation amplitude and phase for accurate cellular control.
Area of Science:
- * Biochemistry and molecular biology of circadian rhythms.
- * Cyanobacterial physiology and gene regulation.
- * Systems biology and computational modeling of biological oscillators.
Background:
- * Circadian rhythms in cyanobacteria are regulated by the KaiABC system.
- * KaiC phosphorylation is a key process in the cyanobacterial circadian clock.
- * Previous studies have initiated experimental and theoretical exploration of KaiC phosphorylation mechanisms.
Purpose of the Study:
- * To investigate the dynamic diversity of hexameric KaiC phosphoforms.
- * To elucidate the mechanism of circadian KaiC phosphorylation in vitro.
- * To understand the role of dual phosphorylation sites (S431 and T432) in KaiC function.
Main Methods:
- * Development of a multi-layer reaction network model.
- * In vitro reconstitution of the KaiABC system.
- * Analysis of phosphorylation dynamics and oscillatory profiles.
Main Results:
- * Demonstrated dynamic diversity in hexameric KaiC phosphoforms due to nonequivalent S431 and T432 sites.
- * Identified a single KaiC hexamer as an energy-based, phosphorylation-dependent circadian oscillator modulated by KaiA and KaiB.
- * Revealed T432 as the primary amplitude regulator and S431 as the major phase regulator, with both sites coordinating the phosphorylation period.
Conclusions:
- * Diverse oscillatory profiles of KaiC phosphoforms generate complex phase modulation patterns, likely driving genome-wide transcription rhythms.
- * The KaiC hexamer functions as a robust, self-regulated circadian oscillator.
- * The Kai oscillator's dynamic diversity and robustness qualify it as a core pacemaker for pervasive and accurate control of cellular processes in cyanobacteria.
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