Legionella is a gram-negative microorganism and an infectious agent of pneumonia in humans. It is an intracellular pathogen and multiplies in different eukaryotic cells like amoebae, ciliated protozoa, macrophages, monocytes, and lung epithelial cells. Proliferation of L. pneumophila in eukaryotic cells depends on its type 4 secretion system, which delivers an arsenal of bacterial effector proteins to cytoplasm of its host. Once within the cytoplasm, effectors modify a broad range of host activities, including mRNA translation. Translation is inhibited by Legionella through the action of several effector proteins including Lgt1, Lgt2, Lgt3, SidI, LegK4, SidL, and RavX. Lgt1-3 and SidI target elongation factors: Lgt1-3 mono-glucosylate elongation factor eEF1A, while SidI binds eEF1A, and eEF1Bγ. Effector LegK4 inhibits protein synthesis by phosphorylating Hsp70 proteins, while SidL and RavX have no defined targets in protein synthesis machinery thus far. In addition to direct inhibition of protein synthesis, SidI also affects the stress response, whereas Lgt1-3 - unfolded protein response and cell-cycle progression of host cells. Whether manipulation of these processes is linked to canonical or non-canonical function(s) of targeted elongation factors remains unknown.

中文翻译：

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肺炎军团菌靶向真核mRNA翻译。

军团菌是革兰氏阴性微生物，是人类肺炎的传染原。它是一种细胞内病原体，可在不同的真核细胞（如变形虫，纤毛原生动物，巨噬细胞，单核细胞和肺上皮细胞）中繁殖。肺炎衣原体在真核细胞中的增殖取决于其4型分泌系统，该系统将细菌效应蛋白的一个库传递至其宿主的细胞质。一旦进入细胞质，效应子就会修饰广泛的宿主活动，包括mRNA翻译。军团菌通过几种效应蛋白（包括Lgt1，Lgt2，Lgt3，SidI，LegK4，SidL和RavX）的作用抑制翻译。Lgt1-3和SidI目标延伸因子：Lgt1-3单葡萄糖基延伸因子eEF1A，而SidI结合eEF1A和eEF1Bγ。效应物LegK4通过磷酸化Hsp70蛋白来抑制蛋白合成，而SidL和RavX迄今为止在蛋白合成机制中尚无明确的靶标。除了直接抑制蛋白质合成外，SidI还影响应激反应，而Lgt1-3-展开的蛋白质反应和宿主细胞的细胞周期进程。这些过程的操纵是否与靶向伸长因子的规范功能或非规范功能相关联仍是未知的。