Noncanonical amino acids form a highly diverse pool of building blocks that can render unique physicochemical properties to peptides and proteins. Here, four methionine analogues with unsaturated and varying side chain lengths were successfully incorporated at four different positions in nisin in Lactococcus lactis through force feeding. This approach allows for residue-specific incorporation of methionine analogues into nisin to expand their structural diversity and alter their activity profiles. Moreover, the insertion of methionine analogues with biorthogonal chemical reactivity, e.g., azidohomoalanine and homopropargylglycine, provides the opportunity for chemical coupling to functional moieties and fluorescent probes as well as for intermolecular coupling of nisin variants. All resulting nisin conjugates retained antimicrobial activity, which substantiates the potential of this method as a tool to further study its localization and mode of action.

中文翻译：

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通过结合甲硫氨酸类似物和随后的点击化学合成和表征异二聚体和荧光乳链菌肽物种。

非经典氨基酸形成高度多样化的构建块池，可以赋予肽和蛋白质独特的物理化学特性。在这里，四种具有不饱和和不同侧链长度的甲硫氨酸类似物被成功地掺入乳酸乳球菌中乳酸链球菌肽的四个不同位置通过强制喂食。这种方法允许将蛋氨酸类似物特定于残基并入乳链菌肽中，以扩大其结构多样性并改变其活性谱。此外，插入具有双正交化学反应性的甲硫氨酸类似物，例如叠氮高丙氨酸和高炔丙基甘氨酸，为与功能部分和荧光探针的化学偶联以及乳酸链球菌肽变体的分子间偶联提供了机会。所有得到的乳链菌肽缀合物都保留了抗菌活性，这证实了该方法作为进一步研究其定位和作用方式的工具的潜力。