Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
School of Chemical Sciences NMR Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
J Am Chem Soc. 2022 Sep 28;144(38):17549-17557. doi: 10.1021/jacs.2c06808. Epub 2022 Sep 15.
Lanthipeptides are a class of cyclic peptides characterized by the presence of one or more lanthionine (Lan) or methyllanthionine (MeLan) thioether rings. These cross-links are produced by α,β-unsaturation of Ser or Thr residues in peptide substrates by dehydration, followed by a Michael-type conjugate addition of Cys residues onto the dehydroamino acids. Lanthipeptides may be broadly classified into at least five different classes, and the biosynthesis of classes I-IV lanthipeptides requires catalysis by LanC cyclases that control both the site-specificity and the stereochemistry of the conjugate addition. In contrast, there are no current examples of LanCs that occur in class V biosynthetic clusters, despite the presence of lanthionine rings in these compounds. In this work, bioinformatics-guided co-occurrence analysis identifies more than 240 putative class V lanthipeptide clusters that contain a LanC cyclase. Reconstitution studies demonstrate that the cyclase-catalyzed product is notably distinct from the product formed spontaneously. Stereochemical analysis shows that the cyclase diverts the final product to a configuration that is distinct from one that is energetically favored. Structural characterization of the final product by multi-dimensional NMR spectroscopy reveals that it forms a helical stapled peptide. Mutational analysis identified a plausible order for cyclization and suggests that enzymatic rerouting to the final structure is largely directed by the construction of the first lanthionine ring. These studies show that lanthipeptide cyclases are needed for the biosynthesis of some constrained peptides, the formations of which would otherwise be energetically unfavored.
硫肽是一类具有一个或多个硫醚环的环肽，其特征为存在一个或多个链霉素（Lan）或甲硫链霉素（MeLan）硫醚环。这些交联是通过在肽底物中 Ser 或 Thr 残基的α,β-不饱和作用脱水，然后 Cys 残基对脱氢氨基酸进行迈克尔型共轭加成产生的。硫肽可广泛分为至少五类，其中 I-IV 类硫肽的生物合成需要 LanC 环化酶的催化，该酶控制共轭加成的特异性和立体化学。相比之下，尽管这些化合物中存在硫醚环，但在 V 类生物合成簇中没有当前的 LanC 例子。在这项工作中，基于生物信息学的共现分析确定了 240 多个含有 LanC 环化酶的假定 V 类硫肽簇。重建研究表明，环化酶催化的产物与自发形成的产物明显不同。立体化学分析表明，环化酶将最终产物转化为一种与能量有利的构型不同的构型。通过多维 NMR 光谱学对最终产物的结构特征进行表征表明，它形成了一种螺旋状的订书肽。突变分析确定了环化的合理顺序，并表明酶对最终结构的重新定向在很大程度上由第一个硫醚环的构建决定。这些研究表明，硫肽环化酶是某些约束肽生物合成所必需的，否则这些肽的形成在能量上是不利的。
