Phase-dependent generation and transmission of time information by the KaiABC circadian clock oscillator through SasA-KaiC interaction in cyanobacteria.
Phase-dependent generation and transmission of time information by the KaiABC circadian clock oscillator through SasA-KaiC interaction in cyanobacteria.
复制标题
KaiABC 生物钟振荡器通过蓝藻中的 SasA-KaiC 相互作用产生和传输时间信息的相位依赖性。
DOI：
10.1111/j.1365-2443.2012.01597.x
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发表时间：
2012
期刊：
影响因子：
2.1
通讯作者：
et al
中科院分区：
文献类型：
--
作者：
Valencia S;J;et al
生物钟允许生物体预测昼夜循环的环境变化。在蓝藻生物钟机制中，时钟蛋白KaiC的磷酸化水平和ATP酶活性以大约24 h的周期振荡。 时间信息通过KaiC的SasA自磷酸化增强活性从KaiC传递到组氨酸激酶SasA，最终导致全基因组转录循环。在这里，我们发现，来自嗜热蓝藻Thermosynechococcus elongatusBP-1的SasA具有正统组氨酸激酶的结构域结构，其C末端结构域（在His 160处含有磷酸化位点）负责SasA的自磷酸化活性以及温度和磷酸化状态依赖性三聚化/六聚化活性。 SasA和KaiC通过其N末端结构域与依赖于其磷酸化状态的亲和力相关联。此外，KaiC的SasA自磷酸化增强活性需要C末端ATP酶催化位点，并取决于其磷酸化状态。我们表明，SasA的磷酸转移活性是必不可少的正常的昼夜基因表达的蓝藻细胞的产生。数值模拟表明，昼夜节律的时间信息（自由磷酸化的SasA）主要是由未磷酸化的KaiC在主观的深夜释放。
Circadian clocks allow organisms to predict environmental changes of the day/night cycle. In the cyanobacterial circadian clock machinery, the phosphorylation level and ATPase activity of the clock protein KaiC oscillate with a period of approximately 24 h. The time information is transmitted from KaiC to the histidine kinase SasA through the SasA autophosphorylation‐enhancing activity of KaiC, ultimately resulting in genome‐wide transcription cycles. Here, we showed that SasA derived from the thermophilic cyanobacteriumThermosynechococcus elongatusBP‐1 has the domain structure of an orthodox histidine kinase and that its C‐terminal domain, which contains a phosphorylation site at His160, is responsible for the autophosphorylation activity and the temperature‐ and phosphorylation state‐dependent trimerization / hexamerization activity of SasA. SasA and KaiC associate through their N‐terminal domains with an affinity that depends on their phosphorylation states. Furthermore, the SasA autophosphorylation‐enhancing activity of KaiC requires the C‐terminal ATPase catalytic site and depends on its phosphorylation state. We show that the phosphotransfer activity of SasA is essential for the generation of normal circadian gene expression in cyanobacterial cells. Numerical simulations suggest that circadian time information (free phosphorylated SasA) is released mainly by unphosphorylated KaiC during the late subjective night.