Molecular Mechanism of Signal Transduction in Prokaryotes

最近，我们证明了在大肠杆菌中出现了一种新的信号转导装置。在这类大肠杆菌信号转导分子中，arcB尤其令人感兴趣，因为这些蛋白是独一无二的，因为它们在其主要氨基酸序列中既包含自动磷酸化的组氨酸位点(或递质模块)，又包含接受磷酸的天冬氨酸位点(或接收器模块)。ArcB最初被描述为参与无氧抑制有氧功能调节子的信号转导。我们证明了ArcB在C-末端除了先前鉴定的真实的组氨酸之外，还有另一个磷酸化的组氨酸位点。对于ArcB，已证明含有组氨酸的C-末端结构域(His-717)可以作为替代磷酸(包含该C-末端区域的ArcB的截断形式以前被指定为ArcB^C)。这种新型的感觉激酶被发现含有两个磷酸化的组氨酸位点和一个接受磷酸的天冬氨酸位点。因此，ArcB最有可能制造一个复杂的磷转移电路。此外，我们的结果支持这样的观点，即ArcB不仅可以作为一个强大的装置来传播多个信号，而且可以通过比之前想象的更复杂的方式来组成信令网络。

Recently we demonstrated the occurrence of a novel device of signal transducers in Escherichia coli. Among such E.coli signal transducers, the arcB is of particular interest, because these proteins are unique in the sense that they contain both an autophosphorylated histidine site (or transmitter module) and a phospho-accepting aspartate site (or receiver module) in their primary amino acid sequences. ArcB was originally characterized as the signal transducer involved in anaerobic repression of regulons of the aerobic function. We demonstrated that ArcB possesses in the C-terminal region another phosphorylated histidine site, in addition to the previously indentified authentic one. It was demonstrated for ArcB that the C-terminal domain containing the histidine (His-717) can function as an alternative phosphodonor (a truncated form of ArcB containing this C-terminal region was previously designated as ArcB^C). This novel type of sensory kinases was revealed to contain two phosphorylated histidine sites together with a phospho-accepting asparatate site. It is therefore most likely that ArcB can make a complex phosphotransfer circuitry. Furthermore, our resuls supported the view that ArcB can serve as a powerful device for not only propagating multi-signals but also making up signaling networks through more sophisticated manners than thought previously.