Attractant binding alters arrangement of chemoreceptor dimers within its cluster at a cell pole
Attractant binding alters arrangement of chemoreceptor dimers within its cluster at a cell pole
复制标题
DOI：
10.1073/pnas.0306660101
复制
发表时间：
2004-03-09
影响因子：
11.1
通讯作者：
Kawagishi, I
中科院分区：
文献类型：
--
作者：
Homma, M;Shiomi, D;Kawagishi, I
许多感觉系统涉及信号放大的多个步骤以产生显著的响应。一种这样的机制可能是跨膜受体的聚集。在细菌的趋化性中，从激酶CheA到反应调节剂CheY的化学计量His-Asp磷酸化中继起着核心作用，化学受体（甲基接受趋化蛋白）与CheA和适配器CheW聚集在一起，位于杆状细胞的极点。这种聚类导致了信号放大通过化学感受器同源二聚体之间的相互作用发生的建议。在这里，通过使用体内二硫键交联试验，我们研究了天冬氨酸化学受体（焦油）的二聚体间的相互作用。将两个半胱氨酸残基引入焦油中：一个在亚基界面，另一个在二聚体的外表面。检测到交联二聚体和更高的低聚物（特别是推导的六聚体），它们的丰度取决于CheA和CheW。配体天冬氨酸显着降低了更高的寡聚体的量，但不影响Tar-GFP的极性定位。因此，天冬氨酸的结合改变了组装的信号传导复合物中焦油二聚体之间的碰撞速率，这很可能是由于二聚体的相对位置或轨迹的变化。这些碰撞可能发生在晶体学预测的二聚体的三聚体内，或者发生在这样的三聚体之间。这些结果与化学感受器二聚体的相互作用参与信号转导的提议是一致的。
Many sensory systems involve multiple steps of signal amplification to produce a significant response. One such mechanism may be the clustering of transmembrane receptors. In bacterial chemotaxis, where a stoichiometric His-Asp phosphorelay from the kinase CheA to the response regulator CheY plays a central role, the chemoreceptors (methyl-accepting chemotaxis proteins) cluster together with CheA and the adaptor CheW, at a pole of a rod-shaped cell. This clustering led to a proposal that signal amplification occurs through an interaction between chemoreceptor homodimers. Here, by using in vivo disulfide crosslinking assays, we examined an interdimer interaction of the aspartate chemoreceptor (Tar). Two cysteine residues were introduced into Tar: one at the subunit interface and the other at the external surface of the dimer. Crosslinked dimers and higher oligomers (especially a deduced hexamer) were detected and their abundance depended on CheA and CheW. The ligand aspartate significantly reduced the amounts of higher oligomers but did not affect the polar localization of Tar-GFP. Thus, the binding of aspartate alters the rate of collisions between Tar dimers in assembled signaling complexes, most likely due to a change in the relative positions or trajectories of the dimers. These collisions could occur within a trimer-of dimers predicted by crystallography, or between such trimers. These results are consistent with the proposal that the interaction of chemoreceptor dimers is involved in signal transduction.