Precise adaptation in bacterial chemotaxis through "assistance neighborhoods"
Precise adaptation in bacterial chemotaxis through "assistance neighborhoods"
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DOI：
10.1073/pnas.0603101103
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发表时间：
2006-08-29
影响因子：
11.1
通讯作者：
Wingreen, Ned S.
中科院分区：
文献类型：
--
作者：
Endres, Robert G.;Wingreen, Ned S.
在大肠杆菌中的趋化网络是值得注意的，因为它对广泛环境浓度范围内多种化学信号浓度的微小相对变化敏感。这种敏感性的关键是一个适应系统，它依赖于化学感受器的特定修饰位点的甲基化和去甲基化(或去酰胺化)，分别由Cher和Cheb酶进行。最近发现，当这些酶与特定的受体捆绑在一起时，可以访问五到七个受体。我们证明了这些“辅助邻域”对于通过化学感受器簇传递信号的模型的精确适应是必要的。与实验一致的是，由不同类型的受体组成的模型簇在很大的化学浓度范围内表现出高的灵敏度和精确的适应性，以及适应的簇对自由能变化的吸引剂尺度的添加/移除的响应。我们预测在大的引诱剂浓度下精确适应的两个极限：要么受体达到完全甲基化并关闭，要么受体饱和并停止对引诱剂的反应，但保持其适应的活性。
The chemotaxis network in Escherichia coli is remarkable for its sensitivity to small relative changes in the concentrations of multiple chemical signals over a broad range of ambient concentrations. Key to this sensitivity is an adaptation system that relies on methylation and demethylation (or deamidation) of specific modification sites of the chemoreceptors by the enzymes CheR and CheB, respectively. It was recently discovered that these enzymes can access five to seven receptors when tethered to a particular receptor. We show that these "assistance neighborhoods" are necessary for precise adaptation in a model for signaling by clusters of chemoreceptors. In agreement with experiment, model clusters composed of receptors of different types exhibit high sensitivity and precise adaptation over a wide range of chemical concentrations and the response of adapted clusters to addition/removal of attractant scales with free-energy change. We predict two limits of precise adaptation at large attractant concentrations: Either receptors reach full methylation and turn off, or receptors become saturated and cease to respond to attractant but retain their adapted activity.