Workgroup Structural Biology of Biosynthetic Enzymes, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarland University, Saarbrücken, Germany.
School of Chemistry, University of Glasgow, Glasgow, UK.
Nat Chem. 2023 Apr;15(4):560-568. doi: 10.1038/s41557-023-01153-w. Epub 2023 Mar 9.
Ribosomally synthesized and post-translationally modified peptide natural products have provided many highly unusual scaffolds. This includes the intriguing alkaloids crocagins, which possess a tetracyclic core structure and whose biosynthesis has remained enigmatic. Here we use in vitro experiments to demonstrate that three proteins, CgnB, CgnC and CgnE, are sufficient for the production of the hallmark tetracyclic crocagin core from the precursor peptide CgnA. The crystal structures of the homologues CgnB and CgnE reveal them to be the founding members of a peptide-binding protein family and allow us to rationalize their distinct functions. We further show that the hydrolase CgnD liberates the crocagin core scaffold, which is subsequently N-methylated by CgnL. These insights allow us to propose a biosynthetic scheme for crocagins. Bioinformatic analyses based on these data led to the discovery of related biosynthetic pathways that may provide access to a structurally diverse family of peptide-derived pyrroloindoline alkaloids.
核糖体合成和翻译后修饰的肽天然产物提供了许多非常不寻常的支架。这包括有趣的生物碱 crocagins，它具有四环核心结构，其生物合成仍然是个谜。在这里，我们使用体外实验证明，三种蛋白质 CgnB、CgnC 和 CgnE 足以从前体肽 CgnA 中产生标志性的四环 crocagin 核心。同源物 CgnB 和 CgnE 的晶体结构表明它们是肽结合蛋白家族的创始成员，并使我们能够合理地解释它们的不同功能。我们进一步表明，水解酶 CgnD 释放 crocagin 核心支架，随后由 CgnL 对其进行 N-甲基化。这些见解使我们能够提出 crocagins 的生物合成方案。基于这些数据的生物信息学分析导致发现了相关的生物合成途径，这些途径可能为结构多样的肽衍生吡咯并吲哚生物碱家族提供了途径。
