Department of Applied Physics, Nagoya University, Nagoya, 464-8603, Japan.
Sci Rep. 2021 Feb 25;11(1):4713. doi: 10.1038/s41598-021-84008-z.
The cyanobacterial circadian clock can be reconstituted by mixing three proteins, KaiA, KaiB, and KaiC, in vitro. In this protein mixture, oscillations of the phosphorylation level of KaiC molecules are synchronized to show the coherent oscillations of the ensemble of many molecules. However, the molecular mechanism of this synchronization has not yet been fully elucidated. In this paper, we explain a theoretical model that considers the multifold feedback relations among the structure and reactions of KaiC. The simulated KaiC hexamers show stochastic switch-like transitions at the level of single molecules, which are synchronized in the ensemble through the sequestration of KaiA into the KaiC-KaiB-KaiA complexes. The proposed mechanism quantitatively reproduces the synchronization that was observed by mixing two solutions oscillating in different phases. The model results suggest that biochemical assays with varying concentrations of KaiA or KaiB can be used to test this hypothesis.
蓝藻生物钟可以通过在体外混合三种蛋白质 KaiA、KaiB 和 KaiC 来重建。在这种蛋白质混合物中，KaiC 分子的磷酸化水平的振荡被同步，以显示许多分子的整体相干振荡。然而，这种同步的分子机制尚未完全阐明。在本文中，我们解释了一个理论模型，该模型考虑了 KaiC 的结构和反应之间的多重反馈关系。模拟的 KaiC 六聚体在单个分子水平上表现出随机的开关样转变，通过将 KaiA 隔离到 KaiC-KaiB-KaiA 复合物中，在整体中实现同步。所提出的机制定量再现了通过混合两个在不同相位振荡的溶液所观察到的同步。该模型结果表明，可以使用具有不同浓度的 KaiA 或 KaiB 的生化测定来检验这一假设。
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