How bacterial pathogens "sweeten" host proteins to avoid immunological responses: structural study of sugar transfer by bacterial virulence factors

抗微生物药物耐药性是对全球健康的最大威胁之一。为了减少感染，我们必须确保仅在适当的情况下使用抗生素。因此，其他非抗生素的方法是受欢迎的，并且需要更好地了解细菌感染的生物学。沙门氏菌和大肠杆菌等病原体注入毒力因子（效应器）来抑制抗微生物宿主反应，促进定植。NleB效应在病原体中高度保守。它将GlcNAc糖残基转移到宿主蛋白（GAPDH， FADD， TRADD），这是一种抑制NF-kB活化和感染细胞凋亡的“甜标签”，阻断宿主的主要抗菌反应。在本项目中，我们将使用先进的核磁共振波谱、分子建模（蛋白质-配体对接、长分子动力学模拟）和其他生物物理技术（ITC）来揭示细菌效应物NleB1、SseK1和SseK2对宿主蛋白质分子识别的原子细节结构特征。这个保守家族的成员可以修饰不同的宿主蛋白，并表现出不同的作用模式来抑制宿主的反应，但有趣的是，它们只在非常少量的氨基酸上有所不同。我们将尝试合理化其精细选择性的分子基础，以及糖转移对与其他宿主蛋白（如TRAF2）相互作用的影响。

Antimicrobial resistance is one of the biggest threats to global health. To reduce it, we must ensure that antibiotics are used only where appropriate. Accordingly, other non-antibiotic approaches are welcome, and a better understanding of the biology of bacterial infections is required. Pathogens such as Salmonella and E. coli inject virulence factors (effectors) to suppress antimicrobial host responses, to promote colonisation. The NleB effector is highly conserved among pathogens. It transfers GlcNAc sugar residues to host proteins (GAPDH, FADD, TRADD), a "sweet tag" that inhibits NF-kB activation and apoptosis of infected cells, blocking major antimicrobial host responses. In this project, we will use advanced NMR spectroscopy, molecular modelling (protein-ligand docking, long molecular dynamics simulations), and other biophysical techniques (ITC) to unveil the structural features at atomic detail of the molecular recognition of host proteins by the bacterial effectors NleB1, SseK1, and SseK2. Members of this conserved family modify different host proteins and exhibit distinct modes of action to suppress host responses, but, interestingly, they differ only in a very small number of amino acids. We will try to rationalise the molecular basis of their exquisite selectivity, and the impact of sugar transfer on the interactions with other host proteins such as TRAF2.