The Legionella effector LtpM is a new type of phosphoinositide-activated glucosyltransferase
The Legionella effector LtpM is a new type of phosphoinositide-activated glucosyltransferase
复制标题
DOI：
10.1074/jbc.ra118.005952
复制
发表时间：
2019-02-22
影响因子：
4.8
通讯作者：
Schroeder, Gunnar Neels
中科院分区：
文献类型：
--
作者：
Levanova, Nadezhda;Mattheis, Corinna;Schroeder, Gunnar Neels
嗜肺军团菌引起军团病，一种严重的肺炎。L.嗜肺菌通过其Dot/Icm（细胞器运输/细胞内增殖缺陷）IV型分泌系统将超过300种效应物易位到宿主细胞中，以使其能够在靶细胞中复制。在这里，我们研究了效应LtpM，这是编码在重组热点在L。嗜肺巴黎。我们发现，C-末端磷酸肌醇3-磷酸（PI 3 P）结合域，也发现在其他无关的效应，目标LtpM的军团菌的空泡和早期和晚期内体。LtpM在酵母中的表达引起细胞毒性。LtpM的N-末端结构域的序列比较和结构同源性建模揭示了与来自细菌Photorhabdus asybiotica的糖基转移酶（GT）毒素PaTox的远程相似性;然而，我们发现LtpM中存在DxN基序，而不是GT-A型糖基转移酶的典型DxD基序，这是酶活性和二价阳离子配位所必需的。使用UDP-葡萄糖作为糖供体，我们表明，纯化的LtpM，但表现出葡萄糖水解酶和autoglosylation活性在体外，并证明PI 3 P结合激活LtpM的葡萄糖基转移酶活性对蛋白质底物。在DxN基序中天冬氨酸或天冬酰胺的取代取消了LtpM的活性。此外，尽管迄今为止鉴定的所有糖基转移酶毒素和效应物都依赖于二价阳离子的存在，但LtpM在它们不存在的情况下具有活性。含有LtpM样GT结构域的蛋白质在其它L.嗜肺菌分离株和物种，表明LtpM是用于破坏宿主的糖基转移酶效应子新家族的第一个成员。
Legionella pneumophila causes Legionnaires' disease, a severe form of pneumonia. L. pneumophila translocates more than 300 effectors into host cells via its Dot/Icm (Defective in organelle trafficking/Intracellular multiplication) type IV secretion system to enable its replication in target cells. Here, we studied the effector LtpM, which is encoded in a recombination hot spot in L. pneumophila Paris. We show that a C-terminal phosphoinositol 3-phosphate (PI3P)-binding domain, also found in otherwise unrelated effectors, targets LtpM to the Legionella-containing vacuole and to early and late endosomes. LtpM expression in yeast caused cytotoxicity. Sequence comparison and structural homology modeling of the N-terminal domain of LtpM uncovered a remote similarity to the glycosyltransferase (GT) toxin PaTox from the bacterium Photorhabdus asymbiotica; however, instead of the canonical DxD motif of GT-A type glycosyltransferases, essential for enzyme activity and divalent cation coordination, we found that a DxN motif is present in LtpM. Using UDP-glucose as sugar donor, we show that purified LtpM nevertheless exhibits glucohydrolase and autoglucosylation activity in vitro and demonstrate that PI3P binding activates LtpM's glucosyltransferase activity toward protein substrates. Substitution of the aspartate or the asparagine in the DxN motif abolished the activity of LtpM. Moreover, whereas all glycosyltransferase toxins and effectors identified so far depend on the presence of divalent cations, LtpM is active in their absence. Proteins containing LtpM-like GT domains are encoded in the genomes of other L. pneumophila isolates and species, suggesting that LtpM is the first member of a novel family of glycosyltransferase effectors employed to subvert hosts.