Circadian rhythms. A protein fold switch joins the circadian oscillator to clock output in cyanobacteria.
Circadian rhythms. A protein fold switch joins the circadian oscillator to clock output in cyanobacteria.
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DOI：
10.1126/science.1260031
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发表时间：
2015-07-17
期刊：
影响因子：
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通讯作者：
LiWang A
中科院分区：
文献类型：
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作者：
Chang YG;Cohen SE;Phong C;Myers WK;Kim YI;Tseng R;Lin J;Zhang L;Boyd JS;Lee Y;Kang S;Lee D;Li S;Britt RD;Rust MJ;Golden SS;LiWang A
生物体适应了昼夜的无情循环，因为它们进化出了称为生物钟的计时系统，该系统以24小时的节奏调节生物活动。蓝细菌的生物钟是由一个三蛋白质振荡器驱动的，该振荡器由KaiA、KaiB和KaiC组成，它们共同产生KaiC磷酸化的昼夜节律。我们发现KaiB在两个不同的三维褶皱之间翻转，并且其罕见的向活跃状态的转变提供了一个时间延迟，该时间延迟是将振荡器的定时与地球自转的定时相匹配所必需的。一旦KaiB转换折叠，它就会结合磷酸化的KaiC并捕获KaiA，启动昼夜节律周期的相变，并调节时钟输出途径的组成部分，提供连接振荡器计时和信号功能的联系。
Organisms are adapted to the relentless cycles of day and night, because they evolved timekeeping systems called circadian clocks, which regulate biological activities with ~24-h rhythms. The clock of cyanobacteria is driven by a three-protein oscillator comprised of KaiA, KaiB, and KaiC, which together generate a circadian rhythm of KaiC phosphorylation. We show that KaiB flips between two distinct three-dimensional folds, and its rare transition to an active state provides a time delay that is required to match the timing of the oscillator to that of earth’s rotation. Once KaiB switches folds, it binds phosphorylated KaiC and captures KaiA, initiating a phase transition of the circadian cycle, and regulates components of the clock-output pathway, providing the link that joins the timekeeping and signaling functions of the oscillator.