Bitbol Anne-Florence, Wingreen Ned S
Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey; Department of Physics, Princeton University, Princeton, New Jersey.
Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey; Department of Molecular Biology, Princeton University, Princeton, New Jersey.
Biophys J. 2015 Mar 10;108(5):1293-305. doi: 10.1016/j.bpj.2015.01.024.
Flagellated bacteria, such as Escherichia coli, perform directed motion in gradients of concentration of attractants and repellents in a process called chemotaxis. The E. coli chemotaxis signaling pathway is a model for signal transduction, but it has unique features. We demonstrate that the need for fast signaling necessitates high abundances of the proteins involved in this pathway. We show that further constraints on the abundances of chemotaxis proteins arise from the requirements of self-assembly both of flagellar motors and of chemoreceptor arrays. All these constraints are specific to chemotaxis, and published data confirm that chemotaxis proteins tend to be more highly expressed than their homologs in other pathways. Employing a chemotaxis pathway model, we show that the gain of the pathway at the level of the response regulator CheY increases with overall chemotaxis protein abundances. This may explain why, at least in one E. coli strain, the abundance of all chemotaxis proteins is higher in media with lower nutrient content. We also demonstrate that the E. coli chemotaxis pathway is particularly robust to abundance variations of the motor protein FliM.
鞭毛细菌，如大肠杆菌，在趋化作用过程中，会在吸引剂和驱避剂浓度梯度中进行定向运动。大肠杆菌趋化信号通路是信号转导的一个模型，但它具有独特的特征。我们证明，快速信号传导的需求使得参与该通路的蛋白质丰度很高。我们表明，对趋化蛋白丰度的进一步限制源于鞭毛马达和化学感受器阵列自组装的要求。所有这些限制都是趋化作用所特有的，已发表的数据证实，趋化蛋白往往比其他通路中的同源蛋白表达水平更高。利用趋化通路模型，我们表明，在响应调节因子CheY水平上，该通路的增益随着整体趋化蛋白丰度的增加而增加。这也许可以解释为什么，至少在一种大肠杆菌菌株中，在营养成分较低的培养基中，所有趋化蛋白的丰度都更高。我们还证明，大肠杆菌趋化通路对马达蛋白FliM的丰度变化特别稳健。
