Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins
Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins
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DOI：
10.1073/pnas.0802868105
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发表时间：
2008-08-26
影响因子：
11.1
通讯作者：
Weis, Robert M.
中科院分区：
文献类型：
--
作者：
Besschetnova, Tatiana Y.;Montefusco, David J.;Weis, Robert M.
所有细胞都具有在脂质双分子层环境中起作用的跨膜信号系统。在大肠杆菌趋化途径中，引诱剂与二维受体阵列和信号蛋白的结合同时抑制相关激酶并刺激受体甲基化，这是一个恢复激酶活性的较慢过程。这两种相反的效应通过一种尚不清楚的物理机制导致了对刺激的强大适应。在这里，我们提供了受体密度对激酶刺激和受体甲基化施加平衡影响的证据。受体信号复合物通过模板定向组装方法在一定的表面浓度范围内重组，并测量激酶和受体甲基化活性。激酶活性和甲基化率都随着表面浓度的变化而显著变化，但以相反的方式：高表面密度制备的样品比低表面密度制备的样品更有效地刺激激酶活性，而低表面密度制备的样品比高表面密度制备的样品产生更高的甲基化率。FRET实验表明，激酶活性的协同变化与膜相关受体结构域排列的变化相一致。密度对受体甲基化和激酶刺激的平衡影响自然导致信号调节模型，该模型与大肠杆菌途径的已知逻辑兼容。密度依赖机制可能是一般的，当两个或多个膜相关过程受到途径元件二维浓度的不同影响时，可能会起作用。
All cells possess transmembrane signaling systems that function in the environment of the lipid bilayer. In the Escherichia coli chemotaxis pathway, the binding of attractants to a two-dimensional array of receptors and signaling proteins simultaneously inhibits an associated kinase and stimulates receptor methylation-a slower process that restores kinase activity. These two opposing effects lead to robust adaptation toward stimuli through a physical mechanism that is not understood. Here, we provide evidence of a counterbalancing influence exerted by receptor density on kinase stimulation and receptor methylation. Receptor signaling complexes were reconstituted over a range of defined surface concentrations by using a template-directed assembly method, and the kinase and receptor methylation activities were measured. Kinase activity and methylation rates were both found to vary significantly with surface concentration-yet in opposite ways: samples prepared at high surface densities stimulated kinase activity more effectively than low-density samples, whereas lower surface densities produced greater methylation rates than higher densities. FRET experiments demonstrated that the cooperative change in kinase activity coincided with a change in the arrangement of the membrane-associated receptor domains. The counterbalancing influence of density on receptor methylation and kinase stimulation leads naturally to a model for signal regulation that is compatible with the known logic of the E. coli pathway. Density-dependent mechanisms are likely to be general and may operate when two or more membrane-related processes are influenced differently by the two-dimensional concentration of pathway elements.