Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037.
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037;
Proc Natl Acad Sci U S A. 2018 Apr 17;115(16):4240-4245. doi: 10.1073/pnas.1801999115. Epub 2018 Apr 2.
The influenza virus hemagglutinin (HA) glycoprotein mediates receptor binding and membrane fusion during viral entry in host cells. Blocking these key steps in viral infection has applications for development of novel antiinfluenza therapeutics as well as vaccines. However, the lack of structural information on how small molecules can gain a foothold in the small, shallow receptor-binding site (RBS) has hindered drug design against this important target on the viral pathogen. Here, we report on the serendipitous crystallization-based discovery of a small-molecule -cyclohexyltaurine, commonly known as the buffering agent CHES, that is able to bind to both group-1 and group-2 HAs of influenza A viruses. X-ray structural characterization of group-1 H5N1 A/Vietnam/1203/2004 (H5/Viet) and group-2 H3N2 A/Hong Kong/1/1968 (H3/HK68) HAs at 2.0-Å and 2.57-Å resolution, respectively, revealed that -cyclohexyltaurine binds to the heart of the conserved HA RBS. -cyclohexyltaurine mimics the binding mode of the natural receptor sialic acid and RBS-targeting bnAbs through formation of similar hydrogen bonds and CH-π interactions with the HA. In H3/HK68, -cyclohexyltaurine also binds to a conserved pocket in the stem region, thereby exhibiting a dual-binding mode in group-2 HAs. These long-awaited structural insights into RBS recognition by a noncarbohydrate-based small molecule enhance our knowledge of how to target this important functional site and can serve as a template to guide the development of novel broad-spectrum small-molecule therapeutics against influenza virus.
流感病毒血凝素 (HA) 糖蛋白在病毒进入宿主细胞的过程中介导受体结合和膜融合。阻断病毒感染中的这些关键步骤，可用于开发新型抗流感治疗药物和疫苗。然而，由于缺乏关于小分子如何在小而浅的受体结合位点 (RBS) 立足的结构信息，阻碍了针对病毒病原体这一重要靶标的药物设计。在这里，我们报告了一种基于结晶的小分子 -环已基牛磺酸（通常称为缓冲剂 CHES）的偶然发现，它能够结合流感 A 病毒的组 1 和组 2 HA。通过 X 射线结构表征，我们分别获得了分辨率为 2.0-Å 和 2.57-Å 的组 1 H5N1 A/Vietnam/1203/2004 (H5/Viet) 和组 2 H3N2 A/Hong Kong/1/1968 (H3/HK68) HA，结果表明 -环已基牛磺酸结合到保守的 HA RBS 的核心。-环已基牛磺酸通过与 HA 形成类似的氢键和 CH-π 相互作用，模拟了天然受体唾液酸和 RBS 靶向 bnAbs 的结合模式。在 H3/HK68 中，-环已基牛磺酸还结合到茎区的一个保守口袋中，从而在组 2 HA 中表现出双重结合模式。这些对非碳水化合物小分子识别 RBS 的结构见解，增强了我们对如何靶向这一重要功能位点的认识，并可作为指导开发针对流感病毒的新型广谱小分子治疗药物的模板。
