LptE binds to and alters the physical state of LPS to catalyze its assembly at the cell surface
LptE binds to and alters the physical state of LPS to catalyze its assembly at the cell surface
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DOI：
10.1073/pnas.1402746111
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发表时间：
2014-07-01
影响因子：
11.1
通讯作者：
Kahne, Daniel
中科院分区：
文献类型：
--
作者：
Malojcic, Goran;Andres, Dorothee;Kahne, Daniel
革兰氏阴性细菌细胞表面脂多糖（LPS）的组装对于它们的生存力是必不可少的，并且通过七蛋白LPS转运（Lpt）途径实现。外膜（OM）脂蛋白LptE和β-桶膜蛋白LptD形成复合物，将LPS组装到OM的外小叶中。我们报告的晶体结构的大肠杆菌OM脂蛋白LptE在2.34埃。该结构揭示了与真核LPS结合蛋白的同源性，并允许预测LPS结合位点，这通过遗传和生物物理实验证实。该位点的特定点突变导致OM生物发生缺陷。我们发现，野生型LptE破坏体外LPS-LPS相互作用，这些突变降低了LptE解聚LPS的能力。透射电子显微镜成像显示，LptE可以破坏LPS聚集体，即使在亚化学计量浓度。我们提出了一个模型，在该模型中，LptE的功能作为一个LPS转移蛋白在OM的易位子在运输过程中分解LPS，使其插入到OM。
The assembly of lipopolysaccharide (LPS) on the surface of Gram-negative bacterial cells is essential for their viability and is achieved by the seven-protein LPS transport (Lpt) pathway. The outer membrane (OM) lipoprotein LptE and the beta-barrel membrane protein LptD form a complex that assembles LPS into the outer leaflet of the OM. We report a crystal structure of the Escherichia coli OM lipoprotein LptE at 2.34 angstrom. The structure reveals homology to eukaryotic LPS-binding proteins and allowed for the prediction of an LPS-binding site, which was confirmed by genetic and biophysical experiments. Specific point mutations at this site lead to defects in OM biogenesis. We show that wild-type LptE disrupts LPS-LPS interactions in vitro and that these mutations decrease the ability of LptE to disaggregate LPS. Transmission electron microscopic imaging shows that LptE can disrupt LPS aggregates even at substoichiometric concentrations. We propose a model in which LptE functions as an LPS transfer protein in the OM translocon by disaggregating LPS during transport to allow for its insertion into the OM.