Helix induction in antimicrobial peptides by alginate in biofilms
Helix induction in antimicrobial peptides by alginate in biofilms
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DOI：
10.1074/jbc.m406044200
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发表时间：
2004-09-10
影响因子：
4.8
通讯作者：
Deber, CM
中科院分区：
文献类型：
--
作者：
Chan, C;Burrows, LL;Deber, CM
细菌胞外多糖可抵御吞噬作用、调理作用和脱水，并作为生物膜中细胞外基质的主要结构成分。它们通过对包括阳离子抗菌肽（CAPs）在内的带正电荷的抗菌剂形成扩散屏障，从而导致与生物膜相关的抗性。我们先前创造了新型的CAPs，其由两侧为赖氨酸残基的非两亲性疏水核心组成，并且在疏水片段中含有一个色氨酸残基作为荧光探针。这种超过特定疏水性阈值的肽会自发插入膜中，在微摩尔浓度下对革兰氏阳性菌和革兰氏阴性菌具有抗菌活性。在此我们表明，由囊性纤维化病原体铜绿假单胞菌分泌的由β - D - 甘露糖醛酸和α - L - 古洛糖醛酸组成的聚合物——藻酸盐，可诱导圆二色光谱检测到的α - 螺旋构象，并且使超过疏水性阈值的肽的色氨酸荧光最大值发生蓝移，这些变化通常在此类肽与非极性（膜）环境结合时观察到。在典型的CAPs——蛙皮素II酰胺和天蚕素P1中也观察到了类似的效应。荧光共振能量转移研究表明，藻酸盐仅在超过疏水性阈值的肽中诱导肽 - 肽结合，这表明亲水性的藻酸盐聚合物对细菌而言起到了一种“辅助膜”的作用，展示了生物膜基质对CAPs的一种独特的保护作用。
Bacterial exopolysaccharides provide protection against phagocytosis, opsonization, and dehydration and act as a major structural component of the extracellular matrix in biofilms. They contribute to biofilm-related resistance by acting as a diffusion barrier to positively charged antimicrobial agents including cationic antimicrobial peptides (CAPs). We previously created novel CAPs consisting of a nonamphipathic hydrophobic core flanked by Lys residues and containing a Trp residue in the hydrophobic segment as a fluorescent probe. Peptides of this type above a specific hydrophobicity threshold insert spontaneously into membranes and have antimicrobial activity against Gram-positive and Gram-negative bacteria at micromolar concentrations. Here we show that alginate, a polymer of beta-D-mannuronate and alpha-L-guluronate secreted by the cystic fibrosis pathogen Pseudomonas aeruginosa, induces an alpha-helical conformation detected by circular dichroism spectroscopy and blue shifts in Trp fluorescence maxima in peptides above the hydrophobicity threshold, changes typically observed upon association of such peptides with nonpolar (membrane) environments. Parallel effects were observed in the archetypical CAPs magainin II amide and cecropin P1. Fluorescence resonance energy transfer studies indicated that alginate induces peptide-peptide association only in peptides above the hydrophobicity threshold, suggesting that the hydrophilic alginate polymer behaves as an "auxiliary membrane" for the bacteria, demonstrating a unique protective role for biofilm matrices against CAPs.