Structural basis for type VI secretion effector recognition by a cognate immunity protein.
Structural basis for type VI secretion effector recognition by a cognate immunity protein.
复制标题
DOI：
10.1371/journal.ppat.1002613
复制
发表时间：
2012
期刊：
影响因子：
6.7
通讯作者：
Mougous JD
中科院分区：
文献类型：
--
作者：
Li M;Le Trong I;Carl MA;Larson ET;Chou S;De Leon JA;Dove SL;Stenkamp RE;Mougous JD
VI型分泌系统（T6SS）已成为细菌间相互作用的重要媒介。来自铜绿假单胞菌的T6SS靶向至少三种效应蛋白，VI型分泌输出1-3 (Tse1-3)，到受体革兰氏阴性细胞。Tse2蛋白是一种细胞质效应物，作为靶细胞增殖的有效抑制剂，因此为铜绿假单胞菌供体细胞提供了明显的适应性优势。P. aeruginosa利用一种专门的免疫蛋白，VI型分泌免疫2 (Tsi2)，来保护内源性和细胞间转移的Tse2。在这里，我们发现T6SS传递的Tse2有效地诱导受体细胞静止，而不是死亡。我们证明，尽管Tsi2和Tse2在细胞质中直接相互作用，但Tsi2对于将毒素靶向到分泌器官是必不可少的。为了深入了解Tse2免疫的分子基础，我们求解了Tsi2的1.00 Å x射线晶体结构。该结构表明Tsi2以二聚体的形式组装，与先前表征的免疫或抗毒素蛋白不同。对缺乏Tse2相互作用的Tsi2突变体的遗传筛选显示，Tsi2同源二聚体界面远端的酸性斑块介导毒素相互作用和免疫。与这一发现一致，我们观察到Tsi2二聚体的不稳定性不影响Tse2相互作用。本研究获得的Tsi2结构和功能的分子洞察揭示了T6效应因子分泌的机制，并表明Tse2-Tsi2效应-免疫对具有区别于先前研究的毒素免疫和毒素-抗毒素系统的特征。细菌物种之间的战争已经持续了超过10亿年。在此期间，他们进化出了许多战胜竞争的途径；其中最近被描述的是VI型分泌系统（T6SS）。铜绿假单胞菌的T6SS是一种复杂的机器，细菌利用它来使邻近的细胞中毒。在该系统输送的毒素中，有输出的VI型分泌物2 （Tse2）。除了作用于竞争生物体外，这种毒素还可以作用于铜绿假单胞菌；因此，生物体合成了一种蛋白质，即VI型分泌免疫2 (Tsi2)，它可以中和毒素。本文详细分析了Tsi2的功能和结构。我们发现，虽然Tsi2与细菌内部的Tse2相互作用并稳定了Tse2，但毒素不需要免疫蛋白到达分泌装置。我们的Tsi2的结构表明该蛋白采用二聚体结构；然而，我们发现它的二聚化并不需要Tse2相互作用。相反，我们的研究结果表明，Tse2与Tsi2的酸性表面相互作用，这与同型二聚体界面相反。我们的研究结果为T6毒素分泌和免疫过程提供了关键的分子见解。
The type VI secretion system (T6SS) has emerged as an important mediator of interbacterial interactions. A T6SS from Pseudomonas aeruginosa targets at least three effector proteins, type VI secretion exported 1–3 (Tse1–3), to recipient Gram-negative cells. The Tse2 protein is a cytoplasmic effector that acts as a potent inhibitor of target cell proliferation, thus providing a pronounced fitness advantage for P. aeruginosa donor cells. P. aeruginosa utilizes a dedicated immunity protein, type VI secretion immunity 2 (Tsi2), to protect against endogenous and intercellularly-transferred Tse2. Here we show that Tse2 delivered by the T6SS efficiently induces quiescence, not death, within recipient cells. We demonstrate that despite direct interaction of Tsi2 and Tse2 in the cytoplasm, Tsi2 is dispensable for targeting the toxin to the secretory apparatus. To gain insights into the molecular basis of Tse2 immunity, we solved the 1.00 Å X-ray crystal structure of Tsi2. The structure shows that Tsi2 assembles as a dimer that does not resemble previously characterized immunity or antitoxin proteins. A genetic screen for Tsi2 mutants deficient in Tse2 interaction revealed an acidic patch distal to the Tsi2 homodimer interface that mediates toxin interaction and immunity. Consistent with this finding, we observed that destabilization of the Tsi2 dimer does not impact Tse2 interaction. The molecular insights into Tsi2 structure and function garnered from this study shed light on the mechanisms of T6 effector secretion, and indicate that the Tse2–Tsi2 effector–immunity pair has features distinguishing it from previously characterized toxin–immunity and toxin–antitoxin systems. Bacterial species have been at war with each other for over a billion years. During this period they have evolved many pathways for besting the competition; one of the most recent of these to be described is the type VI secretion system (T6SS). The T6SS of Pseudomonas aeruginosa is a complex machine that the bacterium uses to intoxicate neighboring cells. Among the toxins this system delivers is type VI secretion exported 2 (Tse2). In addition to acting on competing organisms, this toxin can act on P. aeruginosa; thus, the organism synthesizes a protein, type VI secretion immunity 2 (Tsi2), which neutralizes the toxin. In this paper we dissect the function and structure of Tsi2. We show that although Tsi2 interacts with and stabilizes Tse2 inside the bacterium, the toxin does not require the immunity protein to reach the secretion apparatus. Our structure of Tsi2 shows that the protein adopts a dimeric configuration; however, we find that its dimerization is not required for Tse2 interaction. Instead, our findings indicate that Tse2 interacts with an acidic surface of Tsi2 that is opposite the homodimer interface. Our results provide key molecular insights into the process of T6 toxin secretion and immunity.
登录
查看更多内容
影响因子：
56.9
作者：
HENDRICKSON, WA
通讯作者：
HENDRICKSON, WA
影响因子：
14.9
作者：
Davis IW;Leaver-Fay A;Chen VB;Block JN;Kapral GJ;Wang X;Murray LW;Arendall WB 3rd;Snoeyink J;Richardson JS;Richardson DC
通讯作者：
Richardson DC
影响因子：
16
作者：
Kamada, K;Hanaoka, F
通讯作者：
Hanaoka, F
影响因子：
14.8
作者：
Kelley, Lawrence A.;Sternberg, Michael J. E.
通讯作者：
Sternberg, Michael J. E.
DOI：
10.1073/pnas.0813360106
发表时间：
2009-03-17
影响因子：
11.1
作者：
Leiman, Petr G.;Basler, Marek;Mekalanos, John J.
通讯作者：
Mekalanos, John J.