近日，英国牛津大学Tanmay A.M. Bharat团队解析了完整脂多糖结合细菌表面层的原位结构。2019年12月26日，《细胞》杂志在线发表了这一最新研究成果。

研究人员报道了结合脂多糖的O-抗原的新月形杆菌S层的冷冻电镜结构。使用天然质谱和分子动力学模拟，研究人员推导了细胞中O抗原的长度，并显示了钙如何调节脂多糖结合和S层组装。

最后，研究人员利用细胞电子冷冻断层扫描技术展示了完整S层的近原子分辨率原位结构，从而显示了O抗原尖端的S层排列。S层的完整原子结构显示了细胞层析技术在原位结构生物学中的强大功能，并阐明了在原核生理中具有重要作用的一类非常丰富的自组装分子，这对于合成生物学和表面展示应用具有显著潜力 。

研究人员表示，大多数细菌细胞和所有古细菌细胞都由一层类晶体的、保护性的并且决定细胞形状的蛋白质表面层（S层）所包裹。在革兰氏阴性细菌上，S层通过脂多糖固定在细胞上。

附：英文原文

Title: In Situ Structure of an Intact Lipopolysaccharide-Bound Bacterial Surface Layer

Author: Andriko von Kügelgen, Haiping Tang, Gail G. Hardy, Danguole Kureisaite-Ciziene, Yves V. Brun, Phillip J. Stansfeld, Carol V. Robinson, Tanmay A.M. Bharat

Issue&Volume: December 26, 2019

Abstract: Most bacterial and all archaeal cells are encapsulated by a paracrystalline, protective, and cell-shape-determining proteinaceous surface layer (S-layer). On Gram-negative bacteria, S-layers are anchored to cells via lipopolysaccharide. Here, we report an electron cryomicroscopy structure of the Caulobacter crescentus S-layer bound to the O-antigen of lipopolysaccharide. Using native mass spectrometry and molecular dynamics simulations, we deduce the length of the O-antigen on cells and show how lipopolysaccharide binding and S-layer assembly is regulated by calcium. Finally, we present a near-atomic resolution in situ structure of the complete S-layer using cellular electron cryotomography, showing S-layer arrangement at the tip of the O-antigen. A complete atomic structure of the S-layer shows the power of cellular tomography for in situ structural biology and sheds light on a very abundant class of self-assembling molecules with important roles in prokaryotic physiology with marked potential for synthetic biology and surface-display applications.

DOI: 10.1016/j.cell.2019.12.006

Source: https://www.cell.com/cell/fulltext/S0092-8674(19)31332-7