Magnesium Regulates the Circadian Oscillator in Cyanobacteria
Magnesium Regulates the Circadian Oscillator in Cyanobacteria
复制标题
DOI：
10.1177/0748730419851655
复制
发表时间：
2019-08-01
影响因子：
3.5
通讯作者：
Kim, Yong-Ick
中科院分区：
文献类型：
--
作者：
Jeong, Young M.;Dias, Cristiano;Kim, Yong-Ick
生物钟控制着我们身体的24小时生物节律，影响着许多与时间相关的活动，如睡眠和觉醒。最简单的生物钟在蓝藻中发现，蛋白质KaiA、KaiB和KaiC产生KaiC磷酸化和去磷酸化的自我维持的昼夜节律振荡。KaiA通过结合KaiC的A环来激活KaiC磷酸化，而KaiB通过将KaiA与A环隔离来减弱磷酸化。结构分析表明，镁调节KaiC的磷酸化和去磷酸化，通过解离和关联的催化Glu残基，激活磷酸化和去磷酸化，分别。高镁导致KaiC去磷酸化，而低镁导致KaiC磷酸化。当镁浓度在体外低水平和高水平之间交替时，KaiC单独表现为沙漏计时器。我们认为，一个镁为基础的沙漏计时系统可能已被用于古蓝藻镁稳态建立之前。
The circadian clock controls 24-h biological rhythms in our body, influencing many time-related activities such as sleep and wake. The simplest circadian clock is found in cyanobacteria, with the proteins KaiA, KaiB, and KaiC generating a self-sustained circadian oscillation of KaiC phosphorylation and dephosphorylation. KaiA activates KaiC phosphorylation by binding the A-loop of KaiC, while KaiB attenuates the phosphorylation by sequestering KaiA from the A-loop. Structural analysis revealed that magnesium regulates the phosphorylation and dephosphorylation of KaiC by dissociating from and associating with catalytic Glu residues that activate phosphorylation and dephosphorylation, respectively. High magnesium causes KaiC to dephosphorylate, whereas low magnesium causes KaiC to phosphorylate. KaiC alone behaves as an hourglass timekeeper when the magnesium concentration is alternated between low and high levels in vitro. We suggest that a magnesium-based hourglass timekeeping system may have been used by ancient cyanobacteria before magnesium homeostasis was established.