Fakultät II-Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin, Germany.
Biochemistry. 2011 Oct 4;50(39):8362-73. doi: 10.1021/bi200526q. Epub 2011 Sep 9.
Lantibiotics are peptide antibiotics, realizing their unique secondary structure by posttranslational modifications, the most important one being the formation of the characteristic amino acid lanthionine. Like other ribosomal peptide antibiotics, they are synthesized with an N-terminal leader peptide important for posttranslational processing by modifying enzymes; after peptide maturation, the leader peptide is proteolytically cleaved off. Numerous studies of the leader peptides of class I and II lantibiotics already showed their crucial role in recognition, self-immunity, and extracellular transport. The recently described labyrinthopeptins, members of the family of class III lantibiotics, exhibit the characteristic novel amino acid labionin, which was revealed by elucidation of the structure of labyrinthopeptin A2. The assembly of the labionin motif in the linear peptide chain is mediated by the lyase-kinase-cyclase-type enzyme LabKC through a serine side chain phosphorylation with GTP, elimination of the phosphate group, and a subsequent 2-fold Michael-type addition cyclization. In this work, we systematically investigated for the first time the importance of the leader peptide in the processing of class III lantibiotics using the example of the labyrinthopeptin A2 precursor peptide. In vitro studies with synthetic leader peptide analogues revealed that a conserved N-terminal hydrophobic patch on a putative helical structure is required for the proper peptide processing by the modifying enzyme LabKC. On the other hand, studies showed that the C-terminal part of the leader peptide serves as a spacer between the binding site and active sites for phosphorylation and elimination, thus restricting the number of hydroxy amino acid side chains that could undergo dehydration. Finally, a model for the peptide recognition and processing by the LabKC has been postulated.
类细菌素是一种肽类抗生素，通过翻译后修饰来实现其独特的二级结构，其中最重要的修饰是形成特征性氨基酸羊毛硫氨酸。与其他核糖体肽类抗生素一样，它们是通过修饰酶进行翻译后加工的 N 端前导肽合成的；肽成熟后，前导肽被蛋白水解酶切割。大量关于 I 类和 II 类类细菌素前导肽的研究已经表明它们在识别、自我免疫和细胞外运输中的关键作用。最近描述的迷宫肽，作为 III 类类细菌素家族的成员，表现出特征性的新型氨基酸 labionin，这是通过阐明迷宫肽 A2 的结构揭示的。labionin 基序在线性肽链中的组装是由 lyase-kinase-cyclase 型酶 LabKC 通过丝氨酸侧链磷酸化与 GTP 介导的，磷酸基团的消除，以及随后的 2 倍 Michael 型加成环化。在这项工作中，我们首次系统地研究了类 III 类细菌素前导肽在加工过程中的重要性，以迷宫肽 A2 前体肽为例。使用合成前导肽类似物的体外研究表明，在假定的螺旋结构上保守的 N 端疏水区是修饰酶 LabKC 正确加工肽所必需的。另一方面，研究表明前导肽的 C 端部分作为结合位点和磷酸化及消除活性位点之间的间隔物，从而限制了可以发生脱水的羟基氨基酸侧链的数量。最后，提出了 LabKC 肽识别和加工的模型。
