Bacterial synthesis of vitamin B2 generates a by‐product, 5‐(2‐oxopropylideneamino)‐d‐ribityl‐aminouracil (5‐OP‐RU), with potent immunological properties in mammals, but rapid inactivation in water limits practical uses. This natural product covalently bonds to immunological protein MR1 in antigen presenting cells (APCs), enabling MR1 to traffic to the cell surface, where it interacts with T cell receptors (TCRs) on mucosal associated invariant T lymphocytes (MAIT cells), activating their immunological and antimicrobial properties. Here, we develop several new series of water‐stable compounds tailored for powerful and distinctive immunological functions. We report their water stability, capacity to bind MR1 and traffic it to the cell surface (EC50 17 nM), potent activation (EC50 56 pM) or inhibition (IC50 80 nM) of interacting MAIT cells, and develop compounds with diazirine‐alkyne, biotin, or fluorophore labels for studying cellular MR1. Computer modelling casts new light on the molecular mechanism of activation, revealing that activators are first captured in MR1 via pi‐interactions and H‐bonds, before tighter covalent bonding to Lys43 in MR1. This chemical study advances our molecular understanding of how bacterial metabolites are captured by MR1, influence cell surface expression of MR1, interact and modify human T cells; offering new clues for developing novel vaccine adjuvants, immunotherapeutics, and cancer drugs.

中文翻译：

---

从维生素 B2 生物合成的不稳定细菌代谢物中开发出有效的免疫调节剂

维生素 B2 的细菌合成会产生副产物 5-(2-氧亚丙基氨基)-d-核糖基-氨基尿嘧啶 (5-OP-RU)，它在哺乳动物中具有强大的免疫特性，但在水中快速失活限制了实际用途。这种天然产物与抗原呈递细胞 (APC) 中的免疫蛋白 MR1 共价结合，使 MR1 能够运输到细胞表面，与粘膜相关不变 T 淋巴细胞 (MAIT 细胞) 上的 T 细胞受体 (TCR) 相互作用，激活其免疫功能。和抗菌特性。在这里，我们开发了几个新系列的水稳定性化合物，专为强大而独特的免疫功能而设计。我们报告了它们的水稳定性、结合 MR1 并将其运输到细胞表面的能力 (EC50 17 nM)、对相互作用的 MAIT 细胞的有效激活 (EC50 56 pM) 或抑制 (IC50 80 nM)，并开发了含有二氮丙啶-炔烃的化合物，用于研究细胞 MR1 的生物素或荧光团标记。计算机建模为激活的分子机制提供了新的线索，揭示了激活剂首先通过 pi 相互作用和氢键在 MR1 中被捕获，然后与 MR1 中的 Lys43 形成更紧密的共价键合。这项化学研究增进了我们对 MR1 如何捕获细菌代谢物、如何影响 MR1 的细胞表面表达、如何相互作用和修改人类 T 细胞的分子理解；为开发新型疫苗佐剂、免疫治疗和癌症药物提供新线索。