A sequential program of dual phosphorylation of KaiC as a basis for circadian rhythm in cyanobacteria
A sequential program of dual phosphorylation of KaiC as a basis for circadian rhythm in cyanobacteria
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DOI：
10.1038/sj.emboj.7601832
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发表时间：
2007-09-05
期刊：
影响因子：
11.4
通讯作者：
Kondo, Takao
中科院分区：
文献类型：
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作者：
Nishiwaki, Taeko;Satomi, Yoshinori;Kondo, Takao
蓝藻时钟蛋白 KaiC 的昼夜节律磷酸化周期已在体外重建。 KaiC 中两个磷酸化位点丝氨酸 431 (S431) 和苏氨酸 432 (T432) 的磷酸化谱表明，磷酸化循环包含四个步骤： (i) T432 磷酸化； (ii) S431 磷酸化以生成双磷酸化形式的 KaiC； (iii)T432去磷酸化； (iv)S431去磷酸化。然后我们检查了在一个 KaiC 磷酸化位点引入的突变对完整磷酸化位点的影响。我们发现磷酸化循环中每一步的产物都调节下一步的反应，双磷酸化将KaiC从自激酶转化为自磷酸酶，而完全去磷酸化则具有相反的效果。这些机制是蓝藻昼夜节律产生的基础。我们还发现 KaiA、KaiB 和 KaiC 之间的关联是由 S431 磷酸化引起的，这些相互作用将维持节律的幅度。
The circadian phosphorylation cycle of the cyanobacterial clock protein KaiC has been reconstituted in vitro. The phosphorylation profiles of two phosphorylation sites in KaiC, serine 431 (S431) and threonine 432 (T432), revealed that the phosphorylation cycle contained four steps: (i) T432 phosphorylation; (ii) S431 phosphorylation to generate the double-phosphorylated form of KaiC; (iii) T432 dephosphorylation; and (iv) S431 dephosphorylation. We then examined the effects of mutations introduced at one KaiC phosphorylation site on the intact phosphorylation site. We found that the product of each step in the phosphorylation cycle regulated the reaction in the next step, and that double phosphorylation converted KaiC from an autokinase to an autophosphatase, whereas complete dephosphorylation had the opposite effect. These mechanisms serve as the basis for cyanobacterial circadian rhythm generation. We also found that associations among KaiA, KaiB, and KaiC result from S431 phosphorylation, and these interactions would maintain the amplitude of the rhythm.