Viral fusion protein transmembrane domain adopts β-strand structure to facilitate membrane topological changes for virus-cell fusion
Viral fusion protein transmembrane domain adopts β-strand structure to facilitate membrane topological changes for virus-cell fusion
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DOI：
10.1073/pnas.1501430112
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发表时间：
2015-09-01
影响因子：
11.1
通讯作者：
Hong, Mei
中科院分区：
文献类型：
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作者：
Yao, Hongwei;Lee, Michelle W.;Hong, Mei
HIV gp41和流感血凝素(HA)等病毒融合蛋白的C末端跨膜区(TMD)传统上被认为是蛋白质与细胞膜结合时被动的α螺旋锚定在病毒被膜上。到目前为止，由于这些融合蛋白的高度疏水性，它们的构象、动力学和脂类相互作用一直没有得到高分辨率的结构表征。利用幻角旋转固体核磁共振波谱，我们证明了副流感病毒5(PIV5)融合蛋白的TMD具有脂质依赖的构象以及与膜和水的相互作用。在磷脂酰胆碱(PC)和磷脂酰甘油(PG)膜中，TMD主要为α-螺旋构象，而在磷脂酰乙醇胺(PE)膜中，TMD显著变化为β-链构象。测得的有序参数表明，链段是固定的，因此是齐聚的。P-31核磁共振谱和小角X射线散射(SAXS)数据表明，这种富含β链的构象使PE膜转变为双连续立方相，具有丰富的负高斯曲率，这是半熔融中间体和熔融孔的特征。H-1-P-31二维相关谱和H-2谱表明，无论有无TMD，PE膜的水合程度都比PC膜和PG膜低得多，说明TMD与PE的自然脱水倾向相一致，促进了膜的合并。这些结果提示了一种新的病毒融合模型，在该模型中，TMD以β链为融合构象，积极促进融合过程中膜的拓扑变化。
The C-terminal transmembrane domain (TMD) of viral fusion proteins such as HIV gp41 and influenza hemagglutinin (HA) is traditionally viewed as a passive alpha-helical anchor of the protein to the virus envelope during its merger with the cell membrane. The conformation, dynamics, and lipid interaction of these fusion protein TMDs have so far eluded high-resolution structure characterization because of their highly hydrophobic nature. Using magic-angle-spinning solid-state NMR spectroscopy, we show that the TMD of the parainfluenza virus 5 (PIV5) fusion protein adopts lipid-dependent conformations and interactions with the membrane and water. In phosphatidylcholine (PC) and phosphatidylglycerol (PG) membranes, the TMD is predominantly alpha-helical, but in phosphatidylethanolamine (PE) membranes, the TMD changes significantly to the beta-strand conformation. Measured order parameters indicate that the strand segments are immobilized and thus oligomerized. P-31 NMR spectra and small-angle X-ray scattering (SAXS) data show that this beta-strand-rich conformation converts the PE membrane to a bicontinuous cubic phase, which is rich in negative Gaussian curvature that is characteristic of hemifusion intermediates and fusion pores. H-1-P-31 2D correlation spectra and H-2 spectra show that the PE membrane with or without the TMD is much less hydrated than PC and PG membranes, suggesting that the TMD works with the natural dehydration tendency of PE to facilitate membrane merger. These results suggest a new viral-fusion model in which the TMD actively promotes membrane topological changes during fusion using the beta-strand as the fusogenic conformation.