仿Microcin J25結構的多肽合成及其抗菌性之研究

Abstract

套索胜肽是由細菌等微生物產生的特殊環狀結構分子，在自然界中可做為天然的抗生素，也可在研究上用於開發新型多肽類藥物或作為藥物載體，其複雜的生合成過程及抗菌機制也是當今研究套索胜肽的重要課題之一，然而天然的套索胜肽在收集及純化上有著諸多限制，因此在本篇論文裡會以Microcin J25 (MccJ25) 作為研究的主要目標，並期望發展出一種可化學合成的仿套索胜肽結構，並利用此類胜肽分子來為後續的套索胜肽研究建立基礎。 MccJ25是一種含21個胺基酸且具有特殊套索結構的多肽抗生素，藉由阻止RNA聚合酶反應抑制葛蘭氏陰性菌生長，然而因為其複雜且獨特的結構，MccJ25並不容易藉由化學合成的方式製造出來，因此，我們利用改變胺基酸的序列並對支鏈進行不同的修飾，來合成與MccJ25結構類似的多肽及其片段，並分別測試它們對的RNA聚合酶的抑制效果，試圖找出MccJ25中哪一部分對於其生物活性有較大的重要性。 仿MccJ25的胜肽合成法也能在生物測試上提供了相當大的靈活性，我們可以利用固相合成的方式輕易地改變套索胜肽的胺基酸序列，或是在序列中插入以及減少胺基酸數量，並測試胺基酸的改變對於胜肽對細胞膜之穿透性或抑菌性的影響，藉此來了解套索胜肽在生物體中運作的機制。

Lasso peptides are unique cyclic molecules produced by bacteria and other microorganisms. They function as natural antibiotics in nature and can be used in research for developing novel peptide-based drugs or as drug carriers. The complex biosynthesis process and antibacterial mechanisms of lasso peptides are key areas of current research. However, natural lasso peptides face significant limitations in terms of collection and purification. My thesis focuses on Microcin J25 (MccJ25) as the primary subject of study, aiming to develop a chemically synthesized mimic of the lasso peptide structure. This approach seeks to establish a foundation for future research on lasso peptides using these synthetic peptide molecules. MccJ25 is a peptide containing 21 amino acids with a unique lasso structure. It acts as an antibiotic against Gram-negative bacteria by inhibiting RNA polymerase activity. However, chemical synthesis is very challenging due to its complex structure. Therefore, we synthesized mimics and fragments that are structurally similar to MccJ25 by changing the sequence of amino acids and modifying the side chains. Bioassays were performed to determine which parts of the MccJ25 structure are most important for its biological activity. The synthesis method for mimicking MccJ25 peptides also offers considerable flexibility in biological testing. By employing solid-phase synthesis, we can easily alter the amino acid sequence of lasso peptides, insert or remove amino acids within the sequence, and assess how these changes affect the peptide's cell membrane permeability or antibacterial activity. This approach allows us to gain insights into the mechanisms by which lasso peptides operate within biological systems.