Regulation of aerobic-to-anaerobic transitions by the FNR cycle in Escherichia coli.
Regulation of aerobic-to-anaerobic transitions by the FNR cycle in Escherichia coli.
复制标题
大肠杆菌中 FNR 循环对需氧到厌氧转变的调节。
DOI：
10.1016/j.jmb.2010.02.015
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发表时间：
2010
影响因子：
5.6
通讯作者：
Savageau,MichaelA
中科院分区：
文献类型：
--
作者：
Tolla,DeanA;Savageau,MichaelA
FNR（富马酸硝酸盐还原）蛋白在多种细菌的整体氧反应中起着核心作用。在大肠杆菌中，FNR是需氧和厌氧生长之间转换的主要转录调节因子。FNR的调节通过在依赖于氧的过程中使分子在三种状态之间循环来实现。为了更好地理解这种转录后循环调控机制的本质，我们建立了FNR蛋白及其在大肠杆菌中调控的动力学模型。杆菌该模型的参数值与野生型生物体的实验数据相拟合，并通过成功预测文献中描述的fnr突变株的行为来验证该模型。我们通过确定其对参数值变化的敏感性及其对铁硫簇组装蛋白和蛋白酶ClpXP浓度变化的响应来表征FNR系统的稳态行为。我们还确定了稳态诱导特性，其提供了作为氧浓度的函数的FNR的活性形式的水平的直接估计。结合FNR靶操纵子表达的报告基因测定，该结果给出了活性FNR与其DNA中识别序列结合的平衡解离常数的估计值。最后，我们预测了有氧到厌氧的转变的动态，并确定了不同的贡献，在转录和翻译后水平上运行的调控机制的动态配置文件。
The FNR (fumarate nitrate reduction) protein plays a central role in the global oxygen response of a variety of bacteria. In Escherichia coli, FNR is the master transcriptional regulator of the transition between aerobic and anaerobic growth. Regulation of FNR is achieved by cycling the molecule between three states in a process dependent on oxygen. In an effort to better understand the nature of this post-transcriptional cyclic regulatory mechanism, we formulated a kinetic model of the FNR protein and its regulation in E. coli. The values for the parameters of the model were fit to experimental data for the wild-type organism, and the model was validated by successfully predicting the behavior of fnr mutant strains characterized in the literature. We characterized the steady-state behavior of the FNR system by determining its sensitivity to changes in parameter values and its response to changes in the concentration of iron–sulfur cluster assembly proteins and the protease ClpXP. We also determined the steady-state induction characteristic that provides a direct estimate for the levels of the active form of FNR as a function of oxygen concentration. This result, in combination with reporter assays for expression of FNR target operons, gives an estimate for the equilibrium dissociation constant for the binding of active FNR to its recognition sequences in the DNA. Finally, we predicted the dynamics of the aerobic-to-anaerobic transition and determined distinct contributions to the dynamic profile of regulatory mechanisms operating at the transcriptional and post-translational levels.