Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
PLoS One. 2017 Oct 17;12(10):e0186442. doi: 10.1371/journal.pone.0186442. eCollection 2017.
Antimicrobial peptides are important components of the host innate defense mechanism against invading pathogens, especially for drug-resistant bacteria. In addition to bactericidal activity, the 25 residue peptide TP4 isolated from Nile tilapia also stimulates cell proliferation and regulates the innate immune system in mice. In this report, TP4 hyperpolarized and depolarized the membrane potential of Pseudomonas aeruginosa at sub-lethal and lethal concentrations. It also inhibited and eradicated biofilm formation. The in vitro binding of TP4 to bacterial outer membrane target protein, OprI, was markedly enhanced by a membrane-like surfactant sarkosyl and lipopolysaccharide, which converted TP4 into an α-helix. The solution structure of TP4 in dodecylphosphocholine was solved by NMR analyses. It contained a typical α-helix at residues Phe10-Arg22 and a distorted helical segment at Ile6-Phe10, as well as a hydrophobic core at the N-terminus and a cationic patch at the C-terminus. Residues Ile16, Leu19 and Ile20 in the hydrophobic face of the main helix were critical for the integrity of amphipathic structure, other hydrophobic residues played important roles in hemolytic and bactericidal activities. A model for the assembly of helical TP4 embedded in sarkosyl vesicle is proposed. This study may provide valuable insight for engineering AMPs to have potent bactericidal activity but low hemolytic activity.
抗菌肽是宿主先天防御机制对抗入侵病原体的重要组成部分，特别是针对耐药菌。除了杀菌活性外，从尼罗罗非鱼中分离得到的 25 个残基肽 TP4 还能刺激细胞增殖并调节小鼠的先天免疫系统。在本报告中，TP4 在亚致死和致死浓度下使铜绿假单胞菌的膜电位超极化和去极化。它还抑制并消除生物膜的形成。TP4 与细菌外膜靶蛋白 OprI 的体外结合通过膜类似表面活性剂 Sarkosyl 和脂多糖明显增强，这将 TP4 转化为α-螺旋。通过 NMR 分析解决了 TP4 在十二烷基磷酸胆碱中的溶液结构。它在残基 Phe10-Arg22 处包含典型的α-螺旋，在 Ile6-Phe10 处包含扭曲的螺旋段，以及在 N 端的疏水区和在 C 端的正电荷斑。主螺旋疏水区中的残基 Ile16、Leu19 和 Ile20 对两亲结构的完整性至关重要，其他疏水性残基在溶血和杀菌活性中起重要作用。提出了一种螺旋 TP4 嵌入 Sarkosyl 囊泡的组装模型。这项研究可能为工程抗菌肽提供有价值的见解，使其具有强大的杀菌活性但低溶血活性。
