Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States.
Department of Bioengineering, Stanford University, Stanford, California, United States.
Sci Rep. 2017 Dec 1;7(1):16718. doi: 10.1038/s41598-017-16180-0.
Many organisms rely on antimicrobial peptides (AMPs) as a first line of defense against pathogens. In general, most AMPs are thought to kill bacteria by binding to and disrupting cell membranes. However, certain AMPs instead appear to inhibit biomacromolecule synthesis, while causing less membrane damage. Despite an unclear understanding of mechanism(s), there is considerable interest in mimicking AMPs with stable, synthetic molecules. Antimicrobial N-substituted glycine (peptoid) oligomers ("ampetoids") are structural, functional and mechanistic analogs of helical, cationic AMPs, which offer broad-spectrum antibacterial activity and better therapeutic potential than peptides. Here, we show through quantitative studies of membrane permeabilization, electron microscopy, and soft X-ray tomography that both AMPs and ampetoids trigger extensive and rapid non-specific aggregation of intracellular biomacromolecules that correlates with microbial death. We present data demonstrating that ampetoids are "fast killers", which rapidly aggregate bacterial ribosomes in vitro and in vivo. We suggest intracellular biomass flocculation is a key mechanism of killing for cationic, amphipathic AMPs, which may explain why most AMPs require micromolar concentrations for activity, show significant selectivity for killing bacteria over mammalian cells, and finally, why development of resistance to AMPs is less prevalent than developed resistance to conventional antibiotics.
许多生物依靠抗菌肽 (AMPs) 作为抵御病原体的第一道防线。一般来说，大多数 AMP 被认为通过与细胞膜结合并破坏细胞膜来杀死细菌。然而，某些 AMP 似乎反而抑制生物大分子的合成，同时对膜的破坏较小。尽管对机制（s）的理解还不清楚，但人们对用稳定的合成分子模拟 AMP 有着浓厚的兴趣。抗菌 N-取代甘氨酸（肽）低聚物（“ampetoids”）是螺旋形阳离子 AMP 的结构、功能和机制类似物，具有广谱抗菌活性和比肽更好的治疗潜力。在这里，我们通过对膜通透性、电子显微镜和软 X 射线断层扫描的定量研究表明，AMP 和 ampetoids 都引发了细胞内生物大分子的广泛而快速的非特异性聚集，这与微生物的死亡有关。我们提供的数据表明，ampetoids 是“快速杀手”，它可以在体外和体内快速聚集细菌核糖体。我们提出细胞内生物质絮凝聚集是阳离子、两亲性 AMP 杀死的关键机制，这可以解释为什么大多数 AMP 需要微摩尔浓度才能发挥作用，对杀死细菌表现出显著的选择性，而对哺乳动物细胞的杀伤作用较小，最后，为什么 AMP 耐药性的发展比传统抗生素的耐药性发展要少见。
