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Spatial structure and activity mechanism of a novel spider antimicrobial peptide

机译：一种新型蜘蛛抗菌肽的空间结构和活性机理

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Latarcins (Ltc), linear peptides (ca. 25 amino acid long) isolated from the venom of the Lachesana tarabaevi spider, exhibit a broad-spectrum antibacterial activity, most likely acting on the bacterial plasmatic membrane. We study the structure-activity relationships in the series of these compounds. At the first stage, we investigated the spatial structure of one of the peptides, Ltc2a, and its mode of membrane perturbation. This was done by a combination of experimental and theoretical methods. The approach includes (i) structural study of the peptide by CD spectroscopy in phospholipid liposomes and by H-1 NMR in detergent micelles, (ii) determination of the effect on the liposomes by a dye leakage fluorescent assay and P-31 NMR spectroscopy, (iii) refinement of the NMR-derived spatial structure via Monte Carlo simulations in an implicit water-octanol slab, and (iv) calculation of the molecular hydrophobicity potential. The molecule of Ltc2a was found to consist of two helical regions ( residues 3-9 and 13-21) connected via a poorly ordered fragment. The effect of the peptide on the liposomes suggests the carpet mechanism of the membrane deterioration. This is also supported by the analysis of hydrophobic/hydrophilic characteristics of Ltc2a and homologous antimicrobial peptides. These peptides exhibiting a helix-hinge-helix structural motif are characterized by a distinct and feebly marked amphiphilicity of their N- and C-terminal helices, respectively, and by a hydrophobicity gradient along the peptide chain. The approach we suggested may be useful in studying not only other latarcins but also a wider class of membrane-active peptides.
机译：从Lachesana tarabaevi蜘蛛的毒液中分离出的线性肽Latarcins（Ltc）（约25个氨基酸长）具有广谱抗菌活性，最有可能作用于细菌质膜。我们研究了这些化合物系列中的构效关系。在第一阶段，我们研究了一种肽Ltc2a的空间结构及其膜微扰模式。这是通过实验和理论方法的组合来完成的。该方法包括（i）通过磷脂脂质体中的CD光谱和去污剂胶束中的H-1 NMR对肽进行结构研究，（ii）通过染料渗漏荧光测定法和P-31 NMR光谱测定对脂质体的影响， （iii）通过隐式水辛醇平板中的Monte Carlo模拟改进NMR衍生的空间结构，以及（iv）计算分子疏水性。发现Ltc2a的分子由两个螺旋区域（残基3-9和13-21）组成，这些区域通过顺序不规则的片段连接。肽对脂质体的作用提示了膜变质的地毯机制。 Ltc2a和同源抗菌肽的疏水/亲水特性分析也支持这一点。这些显示出螺旋-铰链-螺旋结构基序的肽分别以其N-末端和C-末端螺旋的明显且微弱的两亲性以及沿着肽链的疏水性梯度为特征。我们建议的方法不仅可以用于研究其他拉塔霉素，而且可以用于更广泛的膜活性肽类。

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