Nonparametric entrainment of the in vitro circadian phosphorylation rhythm of cyanobacterial KaiC by temperature cycle
Nonparametric entrainment of the in vitro circadian phosphorylation rhythm of cyanobacterial KaiC by temperature cycle
复制标题
DOI：
10.1073/pnas.0806741106
复制
发表时间：
2009-02-03
影响因子：
11.1
通讯作者：
Kondo, Takao
中科院分区：
文献类型：
--
作者：
Yoshida, Takuya;Murayama, Yoriko;Kondo, Takao
三种蓝藻Kai蛋白和ATP能够在试管中产生KaiC磷酸化的自主节律。由于该周期近似为24小时，并且在很宽的温度范围内稳定，因此这种节律被认为是蓝藻昼夜节律系统的基本振荡器。我们已经检查了在不同温度周期下的节律，发现它被20-28小时的温度周期稳定地携带。由于周期长度不受温度的影响，因此可以从可能的机制中排除周期变化引起的夹带。相反，温度在30摄氏度和45摄氏度之间变化，反之亦然，以相位依赖的方式改变了节律的相位。基于温度阶跃和温度阶跃的相位响应曲线，采用非参数夹带模型（外部刺激引起的不连续相位跳变）估计了单次温度脉冲引起的相移。预测的相移与实验测量的相移是一致的。接下来，由重复的温度循环引起的连续相移由两个相位响应曲线计算，并与实际夹带的节奏。由于在温度循环的各种组合后观察到的夹带模式与预测相匹配，因此即使在简单的三蛋白质系统中，也可能存在非参数夹带功能。我们还分析了温度循环对蓝藻细胞中KaiC磷酸化的夹带，并发现参数和非参数模型在体内起作用。
The three cyanobacterial Kai proteins and ATP are capable of generating an autonomous rhythm of KaiC phosphorylation in a test tube. As the period is approximate to 24 hours and is stable in a wide temperature range, this rhythm is thought to function as the basic oscillator of the cyanobacterial circadian system. We have examined the rhythm under various temperature cycles and found that it was stably entrained by a temperature cycle of 20-28 hours. As the period length was not altered by temperature, entrainment by period change could be excluded from possible mechanisms. Instead, temperature steps between 30 degrees and 45 degrees C and vice versa shifted the phase of the rhythm in a phase-dependent manner. Based on the phase response curves of the step-up and step-down in temperature, phase shift by single temperature pulse was estimated using a nonparametric entrainment model (discontinuous phase jump by external stimuli). The predicted phase shift was consistent with the experimentally measured phase shift. Next, successive phase shifts caused by repeated temperature cycles were computed by two phase response curves and compared with actual entrainment of the rhythm. As the entrainment pattern observed after various combinations of temperature cycles matched the prediction, it is likely that nonparametric entrainment functions even in the simple three-protein system. We also analyzed entrainment of KaiC phosphorylation by temperature cycle in cyanobacterial cells and found both the parametric and the nonparametric models function in vivo.