Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States.
Department of Molecular Biology , Princeton University , Princeton , New Jersey 08544 , United States.
J Am Chem Soc. 2019 Jan 16;141(2):990-997. doi: 10.1021/jacs.8b11060. Epub 2018 Dec 28.
Ribosomally synthesized and post-translationally modified peptides (RiPPs) are an emerging class of natural products that harbor diverse chemical functionalities, usually introduced via the action of a small number of tailoring enzymes. We have been interested in RiPP biosynthetic gene clusters that encode unusual metalloenzymes, as these may install as yet unknown alterations. Using a new bioinformatic search strategy, we recently identified an array of unexplored RiPP gene clusters that are quorum sensing-regulated and contain one or more uncharacterized radical S-adenosylmethionine (RaS) metalloenzymes. Herein, we investigate the reaction of one of these RaS enzymes and find that it installs an intramolecular β-thioether bond onto its substrate peptide by connecting a Cys-thiol group to the β-carbon of an upstream Asn residue. The enzyme responsible, NxxcB, accepts several amino acids in place of Asn and introduces unnatural β-thioether linkages at unactivated positions. This new transformation adds to the growing list of Nature's peptide macrocyclization strategies and expands the already impressive catalytic repertoire of the RaS enzyme superfamily.
核糖体合成和翻译后修饰肽 (RiPPs) 是一类新兴的天然产物，具有多样化的化学功能，通常通过少数几种修饰酶的作用引入。我们一直对编码不寻常金属酶的 RiPP 生物合成基因簇感兴趣，因为这些酶可能会引入尚未发现的修饰。使用新的生物信息学搜索策略，我们最近鉴定了一系列未被探索的 RiPP 基因簇，这些基因簇受群体感应调控，并且包含一个或多个未被表征的自由基 S-腺苷甲硫氨酸 (RaS) 金属酶。本文中，我们研究了其中一种 RaS 酶的反应，发现它通过将半胱氨酸巯基连接到上游 Asn 残基的β-碳上，将一个分子内的β-硫醚键安装到其底物肽上。负责该反应的酶 NxxcB 可以接受几种氨基酸替代 Asn，并在非活性位置引入非天然的β-硫醚键。这种新的转化增加了自然界中肽大环化策略的不断增长的列表，并扩展了 RaS 酶超家族已经令人印象深刻的催化谱。
