Kentner David, Thiem Sebastian, Hildenbeutel Markus, Sourjik Victor
Zentrum für Molekulare Biologie der Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
Mol Microbiol. 2006 Jul;61(2):407-17. doi: 10.1111/j.1365-2958.2006.05250.x.
Chemotactic stimuli in bacteria are sensed by large sensory complexes, or receptor clusters, that consist of tens of thousands of proteins. Receptor clusters appear to play a key role in signal processing, but their structure remains poorly understood. Here we used fluorescent protein fusions to study in vivo formation of the cluster core, which consists of receptors, a kinase CheA and an assisting protein CheW. We show that receptors aggregate through their cytoplasmic domains even in the absence of other chemotaxis proteins. Clustering is further enhanced by the binding of CheW. Surprisingly, we observed that some fragments of CheA bind receptor clusters well in the absence of CheW, although the latter does assist the binding of full-length CheA. The resulting mode of receptor cluster formation is consistent with an experimentally observed flexible stoichiometry of chemosensory complexes and with assumptions of recently proposed computer models of signal processing in chemotaxis.
细菌中的趋化刺激是由大型感官复合体或受体簇感知的，这些复合体或受体簇由数万个蛋白质组成。受体簇似乎在信号处理中起关键作用，但其结构仍知之甚少。在这里，我们使用荧光蛋白融合来研究簇核心在体内的形成，簇核心由受体、激酶CheA和辅助蛋白CheW组成。我们表明，即使在没有其他趋化蛋白的情况下，受体也会通过其胞质结构域聚集。CheW的结合进一步增强了聚集。令人惊讶的是，我们观察到，在没有CheW的情况下，CheA的一些片段能很好地结合受体簇，尽管后者确实有助于全长CheA的结合。由此产生的受体簇形成模式与实验观察到的化学感应复合体的灵活化学计量以及最近提出的趋化信号处理计算机模型的假设相一致。
