Deciphering the structure activity relationship, mode of action and uptake of isonitrile antibiotics in Gram-negative bacteria

由多重耐药病原菌引起的传染病对公众健康构成了重大威胁。尤其是像鲍曼不动杆菌这样的革兰氏阴性细菌迫切需要开发新药，因为几乎没有治疗选择了。破译针对这些菌株的新抗生素面临以下挑战：目前开发的靶标范围有限，耐药策略多样化，以及细胞膜基本上不透水。因此，需要新的方法来破译新的行动模式(MOA)以及巧妙的吸收策略。过去，天然产物一直是强效抗生素的重要来源，表现出各种结构特征，甚至有助于进入革兰氏阴性细胞。其中许多化合物，尽管有很强的抗生素作用，但还没有得到跟进。鉴于目前研发过程中的干旱，它们的系统表征可能会导致新的MOA和相应的药物。我们最近破译了1948年发现的一种异腈抗生素黄霉素的MOA，它对鲍曼不动杆菌具有很强的NM活性。该分子清除细菌细胞中的游离血红素，从而失调其生物合成，导致氧化应激死亡。在这里，我们想通过构效关系研究来破译黄霉素是如何与血红素结合的。因此，我们的目标是通过合成不同的类似物来开发乙烯基、异腈以及芳香环体系的作用。与血红素的结晶将解开结合模式，为化合物的微调提供合理的依据。此外，我们将注意力转向另一种异腈天然产物抗生素B371，它合成了一种化学探针，并利用我们建立的化学蛋白质组学平台研究了其细胞靶点。由于这种分子在结构上不同，并且确实只含有一个异腈基团，我们预计会有一个不依赖于血红素的MOA。最后，我们使用定制的光探测器来解开异腈在革兰氏阴性细胞中神秘的摄取机制。总体而言，这些研究将有助于更深入地了解迄今被忽视的一组抗生素及其新的MOA。

Infectious diseases caused by multiresistant pathogenic bacteria pose a major threat to public health. Especially Gram-negative bacteria such as Acinetobacter baumannii are of urgent need for novel drug development as almost no treatment options are left. Deciphering new antibiotics against these strains is challenged by the limited scope of currently exploited targets, diverse resistance strategies as well as a largely impermeable cell membrane. Thus, new approaches are needed to decipher novel modes of action (MoA) as well as clever uptake strategies. In the past, natural products have been a great source for potent antibiotics displaying various structural features even facilitating the entry into Gram-negative cells. Many of these compounds, despite potent antibiotic effects, have not been followed up. Given the current drought in the development pipeline their systematic characterization may lead to novel MoAs and corresponding drugs.We recently deciphered the MoA of xanthocillin, an isonitrile antibiotic discovered in 1948, with potent nM activity against A. baumannii. The molecule scavenges free heme in the bacterial cell and thereby dysregulates its biosynthesis leading to death by oxidative stress. We here would like to decipher how xanthocillin binds to heme by structure activity relationship studies. We thus aim to exploit the roles of the vinyl groups, the isonitriles as well as the aromatic ring system by the synthesis of diverse analogs. Crystallization with heme will unravel the binding mode and provide a rational for compound fine tuning. Moreover, we turn our attention to another isonitrile natural product antibiotic, B371, synthesize a chemical probe and investigate its cellular targets with our established chemical proteomic platform. As this molecule is structurally different and does only bear one isonitrile group, we anticipate a heme-independent MoA. Finally, we use tailored photoprobes to unravel the enigmatic uptake mechanisms of isonitriles into Gram-negative cells. Overall, these studies will contribute to a deeper understanding of a so far neglected group of antibiotics and their novel MoA.