Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 112, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
J Virol. 2010 Jan;84(2):1066-75. doi: 10.1128/JVI.01473-09. Epub 2009 Nov 11.
The entry of enveloped viruses into host cells is preceded by membrane fusion, which in paramyxoviruses is triggered by the fusion (F) protein. Refolding of the F protein from a metastable conformation to a highly stable postfusion form is critical for the promotion of fusion, although the mechanism is still not well understood. Here we examined the effects of mutations of individual residues of the F protein of Newcastle disease virus, located at critical regions of the protein, such as the C terminus of the N-terminal heptad repeat (HRA) and the N terminus of the C-terminal heptad repeat (HRB). Seven of the mutants were expressed at the cell surface, showing differences in antibody reactivity in comparison with the F wild type. The N211A, L461A, I463A, and I463F mutants showed a hyperfusogenic phenotype both in syncytium and in dye transfer assays. The four mutants promoted fusion more efficiently at lower temperatures than the wild type did, meaning they probably had lower energy requirements for activation. Moreover, the N211A, I463A, and I463F mutants exhibited hemagglutinin-neuraminidase (HN)-independent activity when influenza virus hemagglutinin (HA) was coexpressed as an attachment protein. The data are discussed in terms of alterations of the refolding pathway and/or the stability of the prefusion and fusion conformations.
包膜病毒进入宿主细胞之前会发生膜融合，副粘病毒的膜融合是由融合（F）蛋白触发的。F 蛋白从亚稳定构象重折叠为高度稳定的融合后构象对于促进融合至关重要，尽管其机制仍未完全理解。在这里，我们研究了位于蛋白关键区域（如 N 端七肽重复区（HRA）的 C 末端和 C 端七肽重复区（HRB）的 N 末端）的纽卡斯尔病病毒 F 蛋白的单个残基突变对病毒的影响。七种突变体在细胞表面表达，与 F 野生型相比，其抗体反应存在差异。N211A、L461A、I463A 和 I463F 突变体在合胞体和染料转移试验中均表现出超融合表型。这四个突变体在较低温度下比野生型更有效地促进融合，这意味着它们可能需要更低的激活能量。此外，当共表达流感病毒血凝素（HA）作为附着蛋白时，N211A、I463A 和 I463F 突变体表现出与神经氨酸酶（HN）无关的活性。这些数据从重折叠途径和/或融合前和融合后构象的稳定性的改变方面进行了讨论。
