Center for Membrane Biology and Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA.
Department of Cell Biology, University of Virginia, Charlottesville, Virginia, USA.
J Virol. 2014 Jun;88(12):6636-49. doi: 10.1128/JVI.00396-14. Epub 2014 Apr 2.
Ebolavirus is an enveloped virus causing severe hemorrhagic fever. Its surface glycoproteins undergo proteolytic cleavage and rearrangements to permit membrane fusion and cell entry. Here we focus on the glycoprotein's internal fusion loop (FL), critical for low-pH-triggered fusion in the endosome. Alanine mutations at L529 and I544 and particularly the L529 I544 double mutation compromised viral entry and fusion. The nuclear magnetic resonance (NMR) structures of the I544A and L529A I544A mutants in lipid environments showed significant disruption of a three-residue scaffold that is required for the formation of a consolidated fusogenic hydrophobic surface at the tip of the FL. Biophysical experiments and molecular simulation revealed the position of the wild-type (WT) FL in membranes and showed the inability of the inactive double mutant to reach this position. Consolidation of hydrophobic residues at the tip of FLs may be a common requirement for internal FLs of class I, II, and III fusion proteins.
Many class I, II, and III viral fusion proteins bear fusion loops for target membrane insertion and fusion. We determined structures of the Ebolavirus fusion loop and found residues critical for forming a consolidated hydrophobic surface, membrane insertion, and viral entry.
埃博拉病毒是一种包膜病毒，可引起严重的出血热。其表面糖蛋白经历蛋白水解切割和重排，以允许膜融合和细胞进入。在这里，我们专注于糖蛋白的内部融合环（FL），这对于内体中低 pH 触发的融合至关重要。L529 和 I544 处的丙氨酸突变，特别是 L529 I544 双突变，损害了病毒进入和融合。在脂质环境中，I544A 和 L529A I544A 突变体的核磁共振（NMR）结构显示，一个三残基支架的显著破坏是形成 FL 尖端统一的融合疏水面所必需的。生物物理实验和分子模拟揭示了野生型（WT）FL 在膜中的位置，并表明失活的双突变体无法达到该位置。FL 尖端疏水性残基的整合可能是 I 类、II 类和 III 类融合蛋白内部 FL 的共同要求。
许多 I 类、II 类和 III 类病毒融合蛋白都具有融合环，用于靶膜插入和融合。我们确定了埃博拉病毒融合环的结构，并发现了形成整合疏水面、膜插入和病毒进入所必需的关键残基。
