埃博拉δ肽是两亲性的,埃博拉病毒编码的40个残基的肽,被称为E40。已经在细胞和脂质囊泡中证明了E40δ肽的膜透化活性,表明E40δ肽可能充当病毒传播蛋白。在阴离子脂质和肽的C末端部分中的二硫键的存在下,肽的裂解活性增加。先前的计算机模拟工作预测该肽显示出部分螺旋结构,但是没有关于E40结构的实验信息。这里,我们使用圆二色性光谱法来报告还原和氧化形式的E40肽在水中的二级结构倾向,洗涤剂胶束,和由中性和阴离子脂质组成的脂质囊泡(POPC和POPG,分别)。结果表明,该肽主要是溶液中的无规卷曲,二硫键对肽构象有很小但可测量的影响。二级结构分析显示出较大的不确定性和对参考数据集的依赖性,在我们的系统中,不能用于在膜环境中准确确定肽的二级结构基序。然而,光谱可用于评估取决于溶剂环境和二硫键的肽的二级结构倾向的相对变化。在POPC-POPG囊泡中,肽从随机卷曲向更结构化的构象转变,这在带负电荷的SDS胶束中甚至更明显。在囊泡中,效果取决于肽-脂质比例,可能是由囊泡表面饱和引起的。两性离子POPC囊泡和DPC胶束的进一步实验表明,曲率和带负电荷的脂质都可以诱导构象的变化,这两种效应是累积的。从Na+离子的静电筛选降低了这种影响。即使在PG-PC囊泡的存在下,肽的氧化形式也显示出略微较低的二级结构倾向并保持更无规的卷曲构象。
The Ebola delta peptide is an amphipathic, 40-residue peptide encoded by the Ebola virus, referred to as E40. The membrane-permeabilising activity of the E40 delta peptide has been demonstrated in cells and lipid vesicles suggesting the E40 delta peptide likely acts as a viroporin. The lytic activity of the peptide increases in the presence of anionic lipids and a disulphide bond in the C-terminal part of the peptide. Previous in silico work predicts the peptide to show a partially helical structure, but there is no experimental information on the structure of E40. Here, we use circular dichroism spectroscopy to report the secondary structure propensities of the reduced and oxidised forms of the E40 peptide in water, detergent micelles, and lipid vesicles composed of neutral and anionic lipids (POPC and POPG, respectively). Results indicate that the peptide is predominately a random coil in solution, and the disulphide bond has a small but measurable effect on peptide conformation. Secondary structure analysis shows large uncertainties and dependence on the reference data set and, in our system, cannot be used to accurately determine the secondary structure motifs of the peptide in membrane environments. Nevertheless, the spectra can be used to assess the relative changes in secondary structure propensities of the peptide depending on the solvent environment and disulphide bond. In POPC-POPG vesicles, the peptide transitions from a random coil towards a more structured conformation, which is even more pronounced in negatively charged SDS micelles. In vesicles, the effect depends on the peptide-lipid ratio, likely resulting from vesicle surface saturation. Further experiments with zwitterionic POPC vesicles and DPC micelles show that both curvature and negatively charged lipids can induce a change in conformation, with the two effects being cumulative. Electrostatic screening from Na+ ions reduced this effect. The oxidised form of the peptide shows a slightly lower propensity for secondary structure and retains a more random coil conformation even in the presence of PG-PC vesicles.