Nanodiscs separate chemoreceptor oligomeric states and reveal their signaling properties
Nanodiscs separate chemoreceptor oligomeric states and reveal their signaling properties
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DOI：
10.1073/pnas.0604988103
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发表时间：
2006-08-01
影响因子：
11.1
通讯作者：
Hazelbauer, Gerald L.
中科院分区：
文献类型：
--
作者：
Boldog, Thomas;Grimme, Stephen;Hazelbauer, Gerald L.
细菌化学感受器是跨膜同源二聚体，其可以形成三聚体、高阶阵列和作为信号复合物的一部分的延伸簇。寡聚体中二聚体的相互作用被认为赋予协同性和交叉受体影响，以及配体结合和改变的激酶活性之间的35倍增益。此外，二聚体之间的高阶相互作用对于观察到的不同受体之间的适应性修饰的辅助模式是必要的。阐明这些特性的机制将需要定义哪些受体功能可以由二聚体执行，哪些需要特定的高阶相互作用。然而，这样的分配一直是不可能的。在这里，我们使用纳米圆盘，一种新兴的技术，用于操纵膜蛋白，制备脂质双层的小颗粒含有一个或只有几个化学受体二聚体。我们发现在单个纳米盘中分离的受体二聚体容易被修饰，结合配体，并进行跨膜信号传导。然而，它们几乎不能激活趋化性组氨酸激酶。相反，最大的激活，从而全面控制激酶优先发生在光盘含有大约三个化学感受器二聚体。激酶激活对每个二聚体的受体数量的急剧依赖性意味着激酶激活和控制的核心结构单元是二聚体的三聚体。因此，我们的观察结果表明，化学感受器跨膜信号不需要寡聚体组织以外的同源二聚体和牵连作为下游信号的单位二聚体的三聚体。
Bacterial chemoreceptors are transmembrane homodimers that can form trimers, higher order arrays, and extended clusters as part of signaling complexes. Interactions of dimers in oligomers are thought to confer cooperativity and cross-receptor influences as well as a 35-fold gain between ligand binding and altered kinase activity. In addition, higher order interactions among dimers are necessary for the observed patterns of assistance in adaptational modification among different receptors. Elucidating mechanisms underlying these properties will require defining which receptor functions can be performed by dimers and which require specific higher order interactions. However, such an assignment has not been possible. Here, we used Nanodiscs, an emerging technology for manipulating membrane proteins, to prepare small particles of lipid bilayer containing one or only a few chemoreceptor dimers. We found that receptor dimers isolated in individual Nanodiscs were readily modified, bound ligand, and performed transmembrane signaling. However, they were hardly able to activate the chemotaxis histidine kinase. Instead, maximal activation and thus full-range control of kinase occurred preferentially in discs containing approximately three chemoreceptor dimers. The sharp dependence of kinase activation on this number of receptors per dimer implies that the core structural unit of kinase activation and control is a trimer of dimers. Thus, our observations demonstrate that chemoreceptor transmembrane signaling does not require oligomeric organization beyond homodimers and implicate a trimer of dimers as the unit of downstream signaling.