Biozentrum, University of Basel, Basel 4056, Switzerland.
Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne 1015, Switzerland.
Sci Adv. 2022 Mar 4;8(9):eabm1122. doi: 10.1126/sciadv.abm1122. Epub 2022 Mar 2.
Phosphocholine molecules decorating bacterial cell wall teichoic acids and outer-membrane lipopolysaccharide have fundamental roles in adhesion to host cells, immune evasion, and persistence. Bacteria carrying the operon that performs phosphocholine decoration synthesize phosphocholine after uptake of the choline precursor by LicB, a conserved transporter among divergent species. is a prominent pathogen where phosphocholine decoration plays a fundamental role in virulence. Here, we present cryo-electron microscopy and crystal structures of LicB, revealing distinct conformational states and describing architectural and mechanistic elements essential to choline import. Together with in vitro and in vivo functional characterization, we found that LicB displays proton-coupled import activity and promiscuous selectivity involved in adaptation to choline deprivation conditions, and describe LicB inhibition by synthetic nanobodies (sybodies). Our results provide previously unknown insights into the molecular mechanism of a key transporter involved in bacterial pathogenesis and establish a basis for inhibition of the phosphocholine modification pathway across bacterial phyla.
磷膦酰胆碱分子修饰细菌细胞壁磷壁酸和外膜脂多糖，在与宿主细胞的黏附、免疫逃逸和持续存在中发挥着重要作用。携带进行磷膦酰胆碱修饰的操纵子的细菌在通过保守转运蛋白 LicB 摄取胆碱前体后合成磷膦酰胆碱，LicB 在不同物种中广泛存在。 是一种重要的病原体，其磷膦酰胆碱修饰在毒力中起着至关重要的作用。在这里，我们展示了 LicB 的冷冻电子显微镜和晶体结构，揭示了不同的构象状态，并描述了对胆碱导入至关重要的结构和机制元素。结合体外和体内功能表征，我们发现 LicB 显示质子偶联的导入活性和涉及适应胆碱缺乏条件的混杂选择性，并描述了合成纳米体（sybodies）对 LicB 的抑制作用。我们的研究结果提供了对参与细菌发病机制的关键转运蛋白的分子机制的全新认识，并为抑制跨细菌门的磷膦酰胆碱修饰途径奠定了基础。
