Departments of Biological Sciences and Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
Proc Natl Acad Sci U S A. 2010 Aug 17;107(33):14805-10. doi: 10.1073/pnas.1002119107. Epub 2010 Aug 2.
Three proteins from cyanobacteria (KaiA, KaiB, and KaiC) can reconstitute circadian oscillations in vitro. At least three molecular properties oscillate during this reaction, namely rhythmic phosphorylation of KaiC, ATP hydrolytic activity of KaiC, and assembly/disassembly of intermolecular complexes among KaiA, KaiB, and KaiC. We found that the intermolecular associations determine key dynamic properties of this in vitro oscillator. For example, mutations within KaiB that alter the rates of binding of KaiB to KaiC also predictably modulate the period of the oscillator. Moreover, we show that KaiA can bind stably to complexes of KaiB and hyperphosphorylated KaiC. Modeling simulations indicate that the function of this binding of KaiA to the KaiB*KaiC complex is to inactivate KaiA's activity, thereby promoting the dephosphorylation phase of the reaction. Therefore, we report here dynamics of interaction of KaiA and KaiB with KaiC that determine the period and amplitude of this in vitro oscillator.
三种来自蓝藻的蛋白质（KaiA、KaiB 和 KaiC）可以在体外重新构成生物钟振荡。在这个反应中，至少有三个分子特性会发生振荡，即 KaiC 的节律性磷酸化、KaiC 的 ATP 水解活性以及 KaiA、KaiB 和 KaiC 之间的分子间复合物的组装/拆卸。我们发现，分子间的相互作用决定了这个体外振荡器的关键动态特性。例如，KaiB 中的突变改变了 KaiB 与 KaiC 结合的速率，也可以预期地调节振荡器的周期。此外，我们表明 KaiA 可以稳定地结合 KaiB 和高磷酸化 KaiC 的复合物。建模模拟表明，KaiA 与 KaiB*KaiC 复合物的这种结合的功能是使 KaiA 的活性失活，从而促进反应的去磷酸化阶段。因此，我们在这里报告了 KaiA 和 KaiB 与 KaiC 的相互作用动力学，这些动力学决定了这个体外振荡器的周期和幅度。
