Murata M, Sugahara Y, Takahashi S, Ohnishi S
Department of Biophysics, Faculty of Science, Kyoto University.
J Biochem. 1987 Oct;102(4):957-62. doi: 10.1093/oxfordjournals.jbchem.a122137.
A twenty amino acid hydrophobic peptide with the same sequence as that of the HA2 N-terminal segment of influenza virus hemagglutinin was synthesized and studied as to its fusion activity. The peptide caused rapid and efficient fusion of egg yolk phosphatidylcholine sonicated vesicles at acidic pH but not at neutral pH. The threshold pH was ca. 6.2 and the maximum fusion occurred at pH 4.8, the half-maximal pH for fusion being 5.6. The pH dependence was similar to that of the parent virus. The fusion efficiency was dependent on the ration of lipid to peptide, increasing with decreasing ratio. The fusion can be rapidly switched on and off by adjusting the pH, to the acidic side and neutral, respectively. The peptide with an acetylated or succinylated N-terminus also showed low pH-induced fusion activity but the pH range was shifted by ca. 1 unit to the acidic side. The results indicate that the HA2 hydrophobic segment in the virus fusion protein is directly involved in the fusion reaction and protonation of the acidic residues in the segment is required for the activity.
合成了一种与流感病毒血凝素HA2 N端片段序列相同的20个氨基酸的疏水肽，并对其融合活性进行了研究。该肽在酸性pH值下能使超声处理的蛋黄磷脂酰胆碱囊泡快速高效融合，而在中性pH值下则不能。阈值pH约为6.2，最大融合发生在pH 4.8，融合的半最大pH为5.6。pH依赖性与亲本病毒相似。融合效率取决于脂质与肽的比例，随比例降低而增加。通过分别将pH调节到酸性和中性，可以快速开启和关闭融合。N端乙酰化或琥珀酰化的肽也显示出低pH诱导的融合活性，但pH范围向酸性侧移动了约1个单位。结果表明，病毒融合蛋白中的HA2疏水片段直接参与融合反应，该片段中酸性残基的质子化是活性所必需的。
