Structure and Function in Antimicrobial Piscidins: Histidine Position, Directionality of Membrane Insertion, and pH-Dependent Permeabilization
Structure and Function in Antimicrobial Piscidins: Histidine Position, Directionality of Membrane Insertion, and pH-Dependent Permeabilization
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DOI：
10.1021/jacs.9b00440
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发表时间：
2019-06-26
影响因子：
15
通讯作者：
Cotten, Myriam L.
中科院分区：
文献类型：
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作者：
Mihailescu, Mihaela;Sorci, Mirco;Cotten, Myriam L.
Piscidins是一种富含组氨酸的抗菌肽，与脂质双分子层相互作用为两亲性α -螺旋。它们在体内酸性和碱性pH值下的活性使它们成为生物医学应用的有希望的模板。本研究的重点是p1和p3，它们都有22个残基长，序列同源性为68%。它们共有三个组氨酸（H3， H4和H11），但p1具有更强的渗透性，具有第四个组氨酸（H17）。本研究探讨了组氨酸相关的两性特性变化如何影响p1和p3的通透性。首先，我们发现p3的渗透能力，而不是p1，在pH 6.0时被强烈抑制，当保守的组氨酸部分带电，H17主要是中性的。其次，我们在低含水量和中性pH下进行的中子衍射测量表明p1的平均构象是高度倾斜的，其c端延伸到相反的小叶中。相比之下，p3是表面结合的，其n端向双层内部倾斜。p1的更深的膜插入与其在完全水化时的行为相关：倾斜能力增强，隐藏组氨酸和c端，诱导膜变薄和缺陷，改变膜的电导和粘弹性。此外，它的ph弹性与H17偏爱的中性态有关。总的来说，这些结果提供了关于组氨酸含量和多肽两致病性差异如何引起膜插入和ph依赖性渗透的不同方向性的机制见解。这项工作的特点是互补的方法，包括染料泄漏测定，核磁共振监测滴定，x射线和中子衍射，定向CD，分子动力学，电化学阻抗谱，表面等离子体共振和石英晶体微平衡耗散。
Piscidins are histidine-enriched antimicrobial peptides that interact with lipid bilayers as amphipathic alpha-helices. Their activity at acidic and basic pH in vivo makes them promising templates for biomedical applications. This study focuses on p1 and p3, both 22-residue-long piscidins with 68% sequence identity. They share three histidines (H3, H4, and H11), but p1, which is significantly more permeabilizing, has a fourth histidine (H17). This study investigates how variations in amphipathic character associated with histidines affect the permeabilization properties of p1 and p3. First, we show that the permeabilization ability of p3, but not p1, is strongly inhibited at pH 6.0 when the conserved histidines are partially charged and H17 is predominantly neutral. Second, our neutron diffraction measurements performed at low water content and neutral pH indicate that the average conformation of p1 is highly tilted, with its C-terminus extending into the opposite leaflet. In contrast, p3 is surface bound with its N-terminal end tilted toward the bilayer interior. The deeper membrane insertion of p1 correlates with its behavior at full hydration: an enhanced ability to tilt, bury its histidines and C-terminus, induce membrane thinning and defects, and alter membrane conductance and viscoelastic properties. Furthermore, its pH-resiliency relates to the neutral state favored by H17. Overall, these results provide mechanistic insights into how differences in the histidine content and amphipathicity of peptides can elicit different directionality of membrane insertion and pH-dependent permeabilization. This work features complementary methods, including dye leakage assays, NMR-monitored titrations, X-ray and neutron diffraction, oriented CD, molecular dynamics, electrochemical impedance spectroscopy, surface plasmon resonance, and quartz crystal microbalance with dissipation.