School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Australia.
Institute of Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia.
Biophys Chem. 2024 Nov;314:107318. doi: 10.1016/j.bpc.2024.107318. Epub 2024 Aug 28.
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.
埃博拉三角洲肽是一种由埃博拉病毒编码的 40 个残基的两亲性肽，称为 E40。E40 德尔塔肽在细胞和脂质体中的膜通透性活性已得到证实，这表明 E40 德尔塔肽可能作为一种病毒孔蛋白发挥作用。在阴离子脂质和肽 C 末端部分的二硫键存在的情况下，肽的裂解活性增加。先前的计算机模拟工作预测该肽显示部分螺旋结构，但没有关于 E40 结构的实验信息。在这里，我们使用圆二色性光谱法报告了还原和氧化形式的 E40 肽在水中、去污剂胶束中和由中性和阴离子脂质（分别为 POPC 和 POPG）组成的脂质体中的二级结构倾向。结果表明，该肽在溶液中主要是无规卷曲，二硫键对肽构象有微小但可测量的影响。二级结构分析表明，存在很大的不确定性，并且依赖于参考数据集，并且在我们的系统中，不能用于准确确定肽在膜环境中的二级结构基序。然而，该光谱可用于评估二级结构倾向随溶剂环境和二硫键变化的相对变化。在 POPC-POPG 囊泡中，肽从无规卷曲向更结构化的构象转变，在带负电荷的 SDS 胶束中甚至更为明显。在囊泡中，这种效应取决于肽-脂质的比例，可能是由于囊泡表面饱和所致。用带正电荷的 POPC 囊泡和 DPC 胶束进行的进一步实验表明，曲率和带负电荷的脂质都可以诱导构象变化，这两种效应是累积的。来自 Na 离子的静电屏蔽降低了这种效应。肽的氧化形式显示出较低的二级结构倾向，即使在存在 PG-PC 囊泡的情况下，也保留了更无规卷曲的构象。
