A molecular mechanism for lipopolysaccharide protection of gram-negative bacteria from antimicrobial peptides
A molecular mechanism for lipopolysaccharide protection of gram-negative bacteria from antimicrobial peptides
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DOI：
10.1074/jbc.m412865200
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发表时间：
2005-03-18
影响因子：
4.8
通讯作者：
Shai, Y
中科院分区：
文献类型：
--
作者：
Papo, N;Shai, Y
阳离子抗菌肽是所有生物和微生物之间的第一道化学屏障。它们的主要目标之一是微生物的细胞质膜。然而，目前尚不清楚为什么一些肽对一种特定的细菌菌株有活性，但对其他菌株没有活性。最近的研究表明，脂多糖（LPS）外膜是第一个保护层，实际上控制肽结合和插入革兰氏阴性菌。为了阐明这些相互作用，我们合成并研究了12-mer两亲性α-螺旋抗菌肽（K5 L7）及其非对映体（4D-K5 L7）（含有4个D-氨基酸）。有趣的是，尽管两种肽都强烈结合LPS双层并破坏细菌细胞质膜，但只有非对映体杀死革兰氏阴性细菌。衰减全反射傅里叶变换红外光谱，CD，和表面等离子体共振光谱显示，只有非对映体穿透的LPS层。相比之下，K5 L7协同结合多糖链和外部磷酸基团。因此，自缔合的K5 L7不能穿过紧密堆积的LPS分子，这由LPS巨单层囊泡的落射荧光研究揭示。如透射电子显微镜所示，通过非对映体诱导LPS混合的能力进一步证明了肽结合模式的差异。除了增加我们对LPS保护细菌的分子基础的理解外，这项研究还提出了一种克服LPS耐药性的潜在策略，它应该有助于设计用于未来治疗目的的抗菌肽。
Cationic antimicrobial peptides serve as the first chemical barrier between all organisms and microbes. One of their main targets is the cytoplasmic membrane of the microorganisms. However, it is not yet clear why some peptides are active against one particular bacterial strain but not against others. Recent studies have suggested that the lipopolysaccharide (LPS) outer membrane is the first protective layer that actually controls peptide binding and insertion into Gram-negative bacteria. In order to shed light on these interactions, we synthesized and investigated a 12-mer amphipathic alpha-helical antimicrobial peptide (K5L7) and its diastereomer (4D-K5L7) (containing four D-amino acids). Interestingly, although both peptides strongly bind LPS bilayers and depolarize bacterial cytoplasmic membranes, only the diastereomer kills Gram-negative bacteria. Attenuated total reflectance Fourier transform infrared, CD, and surface plasmon resonance spectroscopies revealed that only the diastereomer penetrates the LPS layer. In contrast, K5L7 binds cooperatively to the polysaccharide chain and the outer phosphate groups. As a result, the self-associated K5L7 is unable to traverse through the tightly packed LPS molecules, revealed by epifluorescence studies with LPS giant unilamellar vesicles. The difference in the peptides' modes of binding is further demonstrated by the ability of the diastereomer to induce LPS miscellization, as shown by transmission electron microscopy. In addition to increasing our understanding of the molecular basis of the protection of bacteria by LPS, this study presents a potential strategy to overcome resistance by LPS, and it should help in the design of antimicrobial peptides for future therapeutic purposes.