Core unit of chemotaxis signaling complexes
Core unit of chemotaxis signaling complexes
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DOI：
10.1073/pnas.1104824108
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发表时间：
2011-06-07
影响因子：
11.1
通讯作者：
Hazelbauer, Gerald L.
中科院分区：
文献类型：
--
作者：
Li, Mingshan;Hazelbauer, Gerald L.
细菌化学感受器、组氨酸激酶CheA和偶联蛋白CheW形成趋化性信号复合物簇。在信号复合物中，激酶活性增强数百倍，并置于受体控制之下。激活是平衡酶活性所必需的，使得受体控制具有生理学相关效应。因此，激酶活化可以被认为是信号传导复合物的潜在核心活性。我们定义了产生这种活性的最小物理单位，使用来自大肠杆菌的化学感受器焦油，通过插入纳米盘而使其可溶于水，以（i）测量CheA和CheW与受体二聚体的最小激酶激活基团的饱和结合，以及（ii）纯化和表征信号传导复合物的核心单元。纯化的复合物激活激酶几乎以及在分离的天然膜中的受体阵列上形成的信号复合物。纯化的复合物含有两个受体三聚体的二聚体和两个CheW的每个CheA二聚体，与约1：1的CheA：CheW的结合测量确定的比例一致。第二：第二章：1的化学计量意味着，CheA二聚体，酶活性的形式，连接两个化学受体三聚体的二聚体的相互作用的一个CheA原聚体和一个CheW与每个三聚体，组织的具体分子相互作用先前已被确定。核心单元将六个受体二聚体与CheA二聚体相关联，提供足够的能力来解释实验观察到的大部分协同性和二聚体间的影响。我们得出结论，2：第二章：1组织是趋化性信号复合物的核心结构和功能单位，并假定信号复合物的六边形阵列特征是从该单位构建的。
Bacterial chemoreceptors, histidine kinase CheA, and coupling protein CheW form clusters of chemotaxis signaling complexes. In signaling complexes kinase activity is enhanced several hundredfold and placed under receptor control. Activation is necessary to poise enzyme activity such that receptor control has physiologically relevant effects. Thus kinase activation can be considered the underlying core activity of signaling complexes. We defined the minimal physical unit that generates this activity using chemoreceptor Tar from Escherichia coli rendered water soluble by insertion into nanodiscs to (i) measure saturable binding of CheA and CheW to the smallest kinase-activating groups of receptor dimers and (ii) purify and characterize core units of signaling complexes. Purified complexes activated kinase almost as well as signaling complexes formed on arrays of receptors in isolated native membrane. Purified complexes contained two receptor trimers of dimers and two CheW for each CheA dimer, consistent with the approximately 1: 1 CheA: CheW ratio determined by binding measurements. The 2: 2: 1 stoichiometry implied that CheA dimers, the enzymatically active form, connect two chemoreceptor trimers of dimers by interaction of one CheA protomer and a CheW with each trimer, an organization for which specific molecular interactions have previously been identified. The core unit associates six receptor dimers with a CheA dimer, providing sufficient capacity to account for much of the cooperativity and interdimer influence observed experimentally. We conclude that the 2: 2: 1 organization is the core structural and functional unit of chemotaxis signaling complexes and postulate that hexagonal arrays characteristic of signaling complexes are built from this unit.