Structure and organization of the human antimicrobial peptide LL-37 in phospholipid membranes: relevance to the molecular basis for its non-cell-selective activity
Structure and organization of the human antimicrobial peptide LL-37 in phospholipid membranes: relevance to the molecular basis for its non-cell-selective activity
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DOI：
10.1042/0264-6021:3410501
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发表时间：
1999-08-01
影响因子：
4.1
通讯作者：
Shai, Y
中科院分区：
文献类型：
--
作者：
Oren, Z;Lerman, JC;Shai, Y
抗菌肽LL-37属于cathelicidin家族，是首个从人体内分离到的两亲性ct螺旋肽。LL-37被认为在抵抗局部感染和炎症和伤口部位病原体的系统性入侵的第一道防线中发挥重要作用。了解其作用方式可能有助于开发模仿人类免疫系统的抗菌剂。体外研究表明，LL-37对细菌和正常真核细胞都有细胞毒性。为了深入了解其非细胞选择性细胞毒性的机制，我们合成了LL-37，其n端截断形式FF-33，以及它们的荧光衍生物（保留了结构和活性），并对其进行了结构和功能表征。结果显示LL-37与其他天然抗菌肽之间存在一些差异，这可能有助于揭示其体内活性。最有趣的是，LL-37在极低浓度的溶液中以单体和低聚物平衡存在。此外，在溶液中，当与两性离子（模拟哺乳动物膜）和带负电荷的膜（模拟细菌膜）结合时，它具有显著的抗蛋白水解降解能力。结果还表明，n端在蛋白水解抗性和溶血活性中起作用，但在抗菌活性中不起作用。LL-37与带负电荷的膜的作用模式表明，通过“类似地毯”的机制，具有类似洗涤剂的效果。然而，LL-37在两性离子膜中寡聚的能力可能表明在正常的真核细胞中形成了跨膜孔。为了检验这种可能性，我们使用偏振衰减全反射傅立叶变换红外光谱，发现肽主要是α螺旋状的，取向几乎平行于两性离子-脂质膜的表面。这一结果不支持通道形成假说，而是支持类似洗涤剂的作用。
The antimicrobial peptide LL-37 belongs to the cathelicidin family and is the first amphipathic ct-helical peptide isolated from human. LL-37 is considered to play an important role in the first line of defence against local infection and systemic invasion of pathogens at sites of inflammation and wounds. Understanding its mode of action may assist in the development of antimicrobial agents mimicking those of the human immune system. In vitro studies revealed that LL-37 is cytotoxic to both bacterial and normal eukaryotic cells. To gain insight into the mechanism of its non-cell-selective cytotoxicity, we synthesized and structurally and functionally characterized LL-37, its N-terminal truncated form FF-33, and their fluorescent derivatives (which retained structure and activity). The results showed several differences, between LL-37 and other native antimicrobial peptides, that may shed light on its in vivo activities. Most interestingly, LL-37 exists in equilibrium between monomers and oligomers in solution at very low concentrations. Also, it is significantly resistant to proteolytic degradation in solution, and when bound to both zwitterionic (mimicking mammalian membranes) and negatively charged membranes (mimicking bacterial membranes). The results also showed a role for the N-terminus in proteolytic resistance and haemolytic activity, but not in antimicrobial activity. The LL-37 mode of action with negatively charged membranes suggests a detergent-like effect via a 'carpet-like' mechanism. However, the ability of LL-37 to oligomerize in zwitterionic membranes might suggest the formation of a transmembrane pore in normal eukaryotic cells. To examine this possibility we used polarized attenuated total reflectance Fourier-transform infrared spectroscopy and found that the peptide is predominantly alpha-helical and oriented nearly parallel with the surface of zwitterionic-lipid membranes. This result does not support the channel-forming hypothesis, but rather it supports the detergent-like effect.