Cyanobacterial circadian pacemaker: Kai protein complex dynamics in the KaiC phosphorylation cycle in vitro
Cyanobacterial circadian pacemaker: Kai protein complex dynamics in the KaiC phosphorylation cycle in vitro
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DOI：
10.1016/j.molcel.2006.05.039
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发表时间：
2006-07-21
期刊：
影响因子：
16
通讯作者：
Kondo, Takao
中科院分区：
文献类型：
--
作者：
Kageyama, Hakuto;Nishiwaki, Taeko;Kondo, Takao
KaiA、KaiB和KaiC是蓝细菌细长聚球藻PCC 7942中生物钟的必需蛋白。KaiC的磷酸化循环在体外混合三种蛋白质和ATP后发生，被认为是控制昼夜节律系统的主要振荡。我们分析了三种Kai蛋白之间形成的复合物的时间分布。在磷酸化阶段，KaiA主动反复与KaiC结合，促进KaiC磷酸化。KaiC的高水平磷酸化诱导KaiC六聚体与KaiB和KaiA的缔合以开始去磷酸化阶段，这与单体KaiC亚基在六聚体中的改组密切相关。通过减少KaiC磷酸化，KaiB从KaiC解离，重新激活KaiA。我们还证实了类似的模型可以应用于蓝藻细胞。这里提出的分子模型提供了昼夜节律计时系统的机制。
KaiA, KaiB, and KaiC are essential proteins of the circadian clock in the cyanobacterium Synechococcus elongatus PCC 7942. The phosphorylation cycle of KaiC that occurs in vitro after mixing the three proteins and ATP is thought to be the master oscillation governing the circadian system. We analyzed the temporal profile of complexes formed between the three Kai proteins. In the phosphorylation phase, KaiA actively and repeatedly associated with KaiC to promote KaiC phosphorylation. High levels of phosphorylation of KaiC induced the association of the KaiC hexamer with KaiB and inactivate KaiA to begin the dephosphorylation phase, which is closely linked to shuffling of the monomeric KaiC subunits among the hexamer. By reducing KaiC phosphorylation, KaiB dissociated from KaiC, reactivating KaiA. We also confirmed that a similar model can be applied in cyanobacterial cells. The molecular model proposed here provides mechanisms for circadian timing systems.