Shang Dejing, Zhang Qian, Dong Weibing, Liang Hao, Bi Xiaonan
Faculty of Life Science, Liaoning Normal University, Dalian 116081, China; Liaoning Provincial Key Laboratory of Biotechnology and Drug Discovery, Dalian 116081, China.
Faculty of Life Science, Liaoning Normal University, Dalian 116081, China.
Acta Biomater. 2016 Mar;33:153-65. doi: 10.1016/j.actbio.2016.01.019. Epub 2016 Jan 21.
A series of synthesized Trp-containing antimicrobial peptides showed significantly different antimicrobial activity against Gram-negative bacteria despite having similar components and amino acid sequences and the same net positive charge and hydrophobicity. Lipopolysaccharide (LPS) in the outer membrane is a permeability barrier to prevent antimicrobial peptides from crossing into Gram-negative bacteria. We investigated the interaction of five Trp-containing peptides, I1W, I4W, L5W, L11W and L12W, with LPS using circular dichroism (CD), IR spectroscopy, isothermal titration calorimetry (ITC), dynamic light scattering (DLS), zeta-potential measurements and confocal laser scanning microscopy, to address whether bacterial LPS is responsible for the different susceptibilities of Gram-negative bacteria to Trp-containing peptides. Our data indicate that I1W and I4W penetrated the LPS layer and killed Gram-negative bacteria by a "self-promoted uptake" pathway in which the peptides first approach LPS by electrostatic forces and then dissociate LPS micelle. This process results in disorganization of the LPS leaflet and promotes the ability of the peptide to cross the outer membrane into the inner membrane and disrupt the cytoplasmic membrane. Although L5W, L11W and L12W strongly bind to LPS bilayers and depolarize bacterial cytoplasmic membranes, similar to I1W and I4W, they are unable to destabilize LPS aggregates and traverse through the tightly packed LPS molecules. This study increases our understanding of the mechanism of action of these peptides in the LPS outer membrane and will help in the development of a potent broad-spectrum antibiotic for future therapeutic purposes.
Tryptophan (Trp) residues show a strong preference for the interfacial region of biological membranes, and this property endows Trp-containing peptides with the unique ability to interact with the surface of bacterial cell membranes. In this manuscript, we report the membrane interaction of Trp-containing peptide to address whether bacterial LPS is responsible for the different susceptibilities of Gram-negative bacteria to Trp-containing peptides. Based on the data collected, we propose a molecular mechanism for the peptide-LPS interactions that allows the peptides to traverse or prevents them from transversing the LPS layer and the target inner membrane. The data should help in the development of a potent broad-spectrum antibiotic for future therapeutic purposes.
一系列合成的含色氨酸抗菌肽，尽管具有相似的组成成分、氨基酸序列、相同的净正电荷和疏水性，但对革兰氏阴性菌却表现出显著不同的抗菌活性。外膜中的脂多糖（LPS）是一种渗透屏障，可防止抗菌肽进入革兰氏阴性菌。我们使用圆二色性（CD）、红外光谱、等温滴定量热法（ITC）、动态光散射（DLS）、ζ电位测量和共聚焦激光扫描显微镜，研究了五种含色氨酸肽I1W、I4W、L5W、L11W和L12W与LPS的相互作用，以确定细菌LPS是否是革兰氏阴性菌对含色氨酸肽敏感性不同的原因。我们的数据表明，I1W和I4W穿透LPS层并通过“自促进摄取”途径杀死革兰氏阴性菌，在该途径中，肽首先通过静电力接近LPS，然后使LPS胶束解离。这个过程导致LPS小叶无序化，并促进肽穿过外膜进入内膜并破坏细胞质膜的能力。尽管L5W、L11W和L12W与I1W和I4W类似，能强烈结合LPS双层并使细菌细胞质膜去极化，但它们无法使LPS聚集体不稳定，也无法穿过紧密堆积的LPS分子。这项研究增进了我们对这些肽在LPS外膜中作用机制的理解，并将有助于开发一种有效的广谱抗生素用于未来的治疗目的。
色氨酸（Trp）残基对生物膜的界面区域表现出强烈偏好，这种特性赋予含色氨酸肽与细菌细胞膜表面相互作用的独特能力。在本论文中，我们报告了含色氨酸肽的膜相互作用，以确定细菌LPS是否是革兰氏阴性菌对含色氨酸肽敏感性不同的原因。基于收集到的数据，我们提出了肽-LPS相互作用的分子机制，该机制使肽能够穿过或阻止它们穿过LPS层和目标内膜。这些数据应有助于开发一种有效的广谱抗生素用于未来的治疗目的。
