Department of Biochemistry and Biomedical Sciences, the Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, Ontario, Canada, L8S4K1.
Mol Microbiol. 2012 Nov;86(4):765-9. doi: 10.1111/mmi.12034. Epub 2012 Sep 24.
The type II secretion system (T2SS) exports folded proteins from the periplasms of Gram-negative bacteria. The type IV pilus system (T4PS) is a multifunctional machine used for adherence, motility and DNA transfer in bacteria and archaea. Partial sequence identity between the two systems suggests that they are related and might function via a similar mechanism, the dynamic assembly and disassembly of pseudopilus (T2SS) or pilus (T4PS) filaments. The major subunit in each system is thought to form the bulk of the (pseudo)pilus, while minor (low-abundance) subunits have proposed roles in assembly initiation, antagonism of disassembly, or modulation of (pseudo)pilus functional properties. In this issue, Cisneros et al. () extend their previous finding that pseudopilus assembly is primed by the minor pseudopilins, showing that the same proteins can initiate assembly of Escherichia coli T4P. Similarly, they show that the E. coli minor pilins prime the polymerization of T2S pseudopili, although unlike genuine pseudopili, the chimeric filaments did not support secretion. This work reinforces the notion of a common assembly mechanism for the T2S and T4P systems.
II 型分泌系统（T2SS）将折叠蛋白从革兰氏阴性菌的周质中输出。IV 型菌毛系统（T4PS）是一种多功能机器，用于细菌和古菌的粘附、运动和 DNA 转移。这两个系统之间存在部分序列同一性，表明它们是相关的，可能通过类似的机制发挥作用，即假菌毛（T2SS）或菌毛（T4PS）丝的动态组装和拆卸。每个系统中的主要亚基被认为形成（伪）菌毛的大部分，而次要（低丰度）亚基在组装起始、解组装拮抗或调节（伪）菌毛功能特性方面具有作用。在本期杂志中，Cisneros 等人（）扩展了他们之前的发现，即假菌毛组装由次要假菌毛启动，表明相同的蛋白质可以启动大肠杆菌 T4P 的组装。同样，他们表明大肠杆菌的次要菌毛可以启动 T2S 假菌毛的聚合，尽管与真正的假菌毛不同，嵌合丝不支持分泌。这项工作强化了 T2S 和 T4P 系统具有共同组装机制的概念。
