The cyanobacterial clock is controlled via the interplay among KaiA, KaiB, and KaiC, which generate a periodic oscillation of KaiC phosphorylation in the presence of ATP. KaiC forms a homohexamer harboring 12 ATP-binding sites and exerts ATPase activities associated with its autophosphorylation and dephosphorylation. The KaiC nucleotide state is a determining factor of the KaiB-KaiC interaction; however, its relationship with the KaiA-KaiC interaction has not yet been elucidated. With the attempt to address this, our native mass spectrometric analyses indicated that ATP hydrolysis in the KaiC hexamer promotes its interaction with KaiA. Furthermore, our nuclear magnetic resonance spectral data revealed that ATP hydrolysis is coupled with conformational changes in the flexible C-terminal segments of KaiC, which carry KaiA-binding sites. From these data, we conclude that ATP hydrolysis in KaiC is coupled with the exposure of its C-terminal KaiA-binding sites, resulting in its high affinity for KaiA. These findings provide mechanistic insights into the ATP-mediated circadian periodicity.

中文翻译：

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KaiC进行的ATP水解促进了其在蓝细菌生物钟系统中的KaiA结合。

蓝细菌时钟是通过KaiA，KaiB和KaiC之间的相互作用控制的，它们在ATP的存在下会产生KaiC磷酸化的周期性振荡。KaiC形成具有12个ATP结合位点的同型六聚体，并发挥与其自身磷酸化和去磷酸化相关的ATPase活性。KaiC核苷酸状态是KaiB-KaiC相互作用的决定因素；但是，它与KaiA-KaiC交互的关系尚未阐明。为了解决这个问题，我们的原生质谱分析表明，KaiC六聚体中的ATP水解促进了它与KaiA的相互作用。此外，我们的核磁共振光谱数据表明，ATP水解与KaiC的柔性C末端片段的构象变化相结合，这些片段带有KaiA结合位点。根据这些数据，我们得出的结论是KaiC中的ATP水解与其C末端KaiA结合位点的暴露相结合，从而导致其对KaiA的高度亲和力。这些发现提供了对ATP介导的昼夜节律周期性的机械学见解。