Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 33, Pages 14805-14810Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1002119107
Keywords
biological clocks; circadian rhythms; cyanobacteria; protein phosphorylation; modeling
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Funding
- National Institute of General Medical Sciences [GM067152, GM081646]
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Three proteins from cyanobacteria (KaiA, KaiB, and KaiC) can reconstitute circadian oscillations in vitro. At least three molecular properties oscillate during this reaction, namely rhythmic phosphorylation of KaiC, ATP hydrolytic activity of KaiC, and assembly/disassembly of intermolecular complexes among KaiA, KaiB, and KaiC. We found that the intermolecular associations determine key dynamic properties of this in vitro oscillator. For example, mutations within KaiB that alter the rates of binding of KaiB to KaiC also predictably modulate the period of the oscillator. Moreover, we show that KaiA can bind stably to complexes of KaiB and hyper-phosphorylated KaiC. Modeling simulations indicate that the function of this binding of KaiA to the KaiB.KaiC complex is to inactivate KaiA's activity, thereby promoting the dephosphorylation phase of the reaction. Therefore, we report here dynamics of interaction of KaiA and KaiB with KaiC that determine the period and amplitude of this in vitro oscillator.
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