Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland.
Department of Biochemistry, Molecular Biology, and Biophysics and BioTechnology Institute, University of Minnesota-Twin Cities, St Paul, Minnesota 55108, USA.
Nat Chem. 2017 Apr;9(4):387-395. doi: 10.1038/nchem.2666. Epub 2016 Nov 28.
Uncultivated bacteria represent a massive resource of new enzymes and bioactive metabolites, but such bacteria remain functionally enigmatic. Polytheonamides are potent peptide cytotoxins produced by uncultivated bacteria that exist as symbionts in a marine sponge. Outside glycobiology, polytheonamides represent the most heavily post-translationally modified biomolecules that are derived from amino acids. The biosynthesis of polytheonamides involves up to 50 site-specific modifications to create a membrane-spanning β-helical structure. Here, we provide functional evidence that only seven enzymes are necessary for this process. They iteratively catalyse epimerization, methylation and hydroxylation of diverse amino acids. To reconstitute C-methylation, we employed the rarely used heterologous host Rhizobium leguminosarum to invoke the activities of two cobalamin-dependent C-methyltransferases. We observed 44 of the modifications to systematically unravel the biosynthesis of one of the most densely modified and metabolically obscure ribosome-derived molecules found in nature.
未培养细菌代表了大量新酶和生物活性代谢物的资源，但这些细菌在功能上仍然是神秘的。聚醚肽是由未培养细菌产生的强效肽细胞毒素，它们作为海洋海绵的共生体存在。在糖生物学之外，聚醚肽代表了最广泛的翻译后修饰的生物分子，这些生物分子来源于氨基酸。聚醚肽的生物合成涉及多达 50 个位点特异性修饰，以创建一个跨膜β-螺旋结构。在这里，我们提供了功能证据，表明这个过程只需要七种酶。它们迭代地催化各种氨基酸的差向异构化、甲基化和羟化。为了重新构建 C-甲基化，我们采用了很少使用的异源宿主根瘤菌来调用两种钴胺素依赖的 C-甲基转移酶的活性。我们观察到 44 种修饰，系统地揭示了自然界中发现的最密集修饰和代谢最不明显的核糖体衍生分子之一的生物合成。
