Cross-scale analysis of temperature compensation in the cyanobacterial circadian clock system
Cross-scale analysis of temperature compensation in the cyanobacterial circadian clock system
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DOI：
10.1038/s42005-022-00852-z
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发表时间：
2022-04-04
影响因子：
5.5
通讯作者：
Akiyama, Shuji
中科院分区：
文献类型：
--
作者：
Furuike, Yoshihiko;Ouyang, Dongyan;Akiyama, Shuji
昼夜节律钟蛋白经常表现出温度补偿反应，抵消温度影响，以保持其酶活性在生理温度范围内恒定。这种反应水平的温度补偿能力可能对生物钟系统至关重要，生物钟蛋白与生物钟系统结合，以实现振荡频率的系统级温度补偿。然而，温度补偿仍然是一个令人困惑的现象，因为在更高的温度下，由于更大的热能，构成时钟蛋白质的侧链波动更频繁。在这里，我们研究了温度对KaiC动力学的影响，KaiC是一种温度补偿酶（ATP酶），在蓝藻生物钟系统中将ATP水解成ADP，使用准弹性中子散射。温度升高10℃，KaiC中皮秒到亚纳秒非相干局部运动的频率仅增加1.2倍。这种局部运动的温度不敏感性不一定是KaiC所独有的，但也证实了KaiC的一系列温度敏感突变体和时钟相关蛋白以外的蛋白质。相反，与反应和系统水平的温度补偿性质相关的动力学在全局扩散运动中被发现，这可能通过改变KaiC的六聚体构象来调节atp酶活性和去磷酸化过程的温度依赖性。建立温度敏感性的跨尺度因果关系的时空尺度是有限的，并且仅在KaiC的非常有限的部分扩展到皮秒到亚纳秒动力学，而不是整个部分。生物钟蛋白补偿温度变化以维持正常运作的机制尚不清楚。这里，从反应到细胞水平的温度补偿可以用中子散射光谱观察到的时钟蛋白内部的大规模运动来解释。
Circadian clock proteins often reveal temperature-compensatory responses that counteract temperature influences to keep their enzymatic activities constant over a physiological range of temperature. This temperature-compensating ability at the reaction level is likely crucial for circadian clock systems, to which the clock proteins are incorporated, to achieve the system-level temperature compensation of the oscillation frequency. Nevertheless, temperature compensation is yet a puzzling phenomenon, since side chains that make up the clock proteins fluctuate more frequently due to greater thermal energy at higher temperature. Here, we investigated temperature influences on the dynamics of KaiC, a temperature-compensated enzyme (ATPase) that hydrolyzes ATP into ADP in the cyanobacterial circadian clock system, using quasielastic neutron scattering. The frequency of picosecond to sub-nanosecond incoherent local motions in KaiC was accelerated by a factor of only 1.2 by increasing the temperature by 10 degrees C. This temperature insensitivity of the local motions was not necessarily unique to KaiC, but confirmed also for a series of temperature-sensitive mutants of KaiC and proteins other than clock-related proteins. Rather, the dynamics associated with the temperature-compensatory nature of the reaction- and system-level was found in global diffusional motions, which was suggested to regulate the temperature dependence of ATPase activity and dephosphorylation process presumably through changes in the hexamer conformation of KaiC. The spatiotemporal scale at which cross-scale causality of the temperature sensitivity is established is finite, and extends down to picosecond to sub-nanosecond dynamics only in a very limited part of KaiC, not in its entire part.The mechanism by which circadian clock proteins compensate for changes in temperature to maintain regular operation remains unclear. Here, temperature compensation from the reaction to cell level is explained by large-scale motions inside the clock protein observed via neutron scattering spectroscopy.