Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
Protein Sci. 2019 May;28(5):971-975. doi: 10.1002/pro.3597. Epub 2019 Apr 1.
The bacterial type VI secretion system (T6SS) utilizes many toxic effectors to gain advantage over interbacterial competition and eukaryotic host infection. Meanwhile, the cognate immunity proteins of these effectors are employed to protect themselves from the virulence. TseT and TsiT form an effector-immunity (E-I) protein pair secreted by T6SS of Pseudomonas aeruginosa. TseT is toxic for other bacteria, whereas TsiT can suppress the virulence of TseT. Here, we report the crystal structure of TsiT at 1.6 Å resolution. TsiT is a typical α + β class protein and belongs to a novel Imm52 protein family of the polymorphic toxin system. Apart from TsiT, only one structure of the Imm52 family proteins is present in the Protein Data Bank (PDB), but that structure is not characterized and shares low sequence identity with TsiT. We characterized the basic features of TsiT structure and identified conserved residues of the Imm52 family proteins according to homology comparison. Our work provided structural information of a new protein family and should aid future functional studies.
细菌的 VI 型分泌系统 (T6SS) 利用许多毒性效应器来获得细菌间竞争和真核宿主感染的优势。同时，这些效应器的同源免疫蛋白被用来保护自己免受毒性的侵害。TseT 和 TsiT 形成由铜绿假单胞菌 T6SS 分泌的效应器-免疫（E-I）蛋白对。TseT 对其他细菌有毒，而 TsiT 可以抑制 TseT 的毒力。在这里，我们报告了 TsiT 在 1.6 Å 分辨率下的晶体结构。TsiT 是一种典型的 α + β 类蛋白，属于多态性毒素系统的 Imm52 蛋白家族的一个新成员。除了 TsiT，蛋白质数据库（PDB）中只有一个 Imm52 家族蛋白的结构，但该结构没有特征，与 TsiT 的序列同一性较低。我们根据同源性比较，对 TsiT 结构的基本特征进行了表征，并确定了 Imm52 家族蛋白的保守残基。我们的工作提供了一个新蛋白家族的结构信息，应该有助于未来的功能研究。
