一阶区的Goldbeter-Koshland开关及其对动力学无序的响应
The Goldbeter-Koshland switch in the first-order region and its response to dynamic disorder
摘要：
在他们的经典作品（Proc. Natl. Acad. Sci. USA，1981，78：6840-6844），Goldbeter和Koshland数学分析了对效应物浓度高度敏感的可逆共价修饰系统。它的信号响应曲线呈S形，构成了一个生化开关。然而，开关行为只出现在“零级区域”，即当信号分子浓度远低于它修饰的底物的浓度时。在这项工作中，我们表明，开关行为也可以发生在可比浓度的信号和底物，提供的信号分子催化的修饰反应的合作。我们还研究了动态障碍对建议的生化开关的影响，其中酶促反应速率，而不是常数，出现作为时间的随机函数。我们表明，该系统是强大的动态无序在散装浓度。但如果动态无序是准静态的，则在低浓度下可以观察到开关响应行为的大波动。这种波动与许多生物功能有关。它可以通过增加蛋白质的构象互变率或关联网络中的酶促反应速率来降低。
英文摘要：
In their classical work (Proc. Natl. Acad. Sci. USA, 1981, 78:6840-6844), Goldbeter and Koshland mathematically analyzed a reversible covalent modification system which is highly sensitive to the concentration of effectors. Its signal-response curve appears sigmoidal, constituting a biochemical switch. However, the switch behavior only emerges in the "zero-order region", i.e. when the signal molecule concentration is much lower than that of the substrate it modifies. In this work we showed that the switching behavior can also occur under comparable concentrations of signals and substrates, provided that the signal molecules catalyze the modification reaction in cooperation. We also studied the effect of dynamic disorders on the proposed biochemical switch, in which the enzymatic reaction rates, instead of constant, appear as stochastic functions of time. We showed that the system is robust to dynamic disorder at bulk concentration. But if the dynamic disorder is quasi-static, large fluctuations of the switch response behavior may be observed at low concentrations. Such fluctuation is relevant to many biological functions. It can be reduced by either increasing the conformation interconversion rate of the protein, or correlating the enzymatic reaction rates in the network.
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