The Transmembrane Conformation of the Influenza B Virus M2 Protein in Lipid Bilayers
The Transmembrane Conformation of the Influenza B Virus M2 Protein in Lipid Bilayers
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DOI：
10.1038/s41598-019-40217-1
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发表时间：
2019-03-06
影响因子：
4.6
通讯作者：
Hong, Mei
中科院分区：
文献类型：
--
作者：
Mandala, Venkata S.;Liao, Shu-Yu;Hong, Mei
甲型和B型流感病毒引起季节性流感流行。B型流感病毒（BM 2）的M2蛋白是一种膜包埋的四聚体质子通道，对病毒的生命周期至关重要。BM 2是AM 2的功能类似物，但与跨膜（TM）结构域仅共享24%的序列同一性。两种抗病毒药物靶向的AM 2的结构和功能已得到很好的表征。相比之下，对BM 2的结构知之甚少，迄今为止还没有药物可以抑制这种蛋白质。在这里，我们使用固态核磁共振光谱研究在高pH值的磷脂双层，这对应于通道的封闭状态的BM 2（1-51）的构象。使用2D和3D相关NMR实验，我们解决并分配TM结构域的29个残基的C-13和N-15化学位移，这产生了骨架（phi，psi）扭转角。残基6-28形成有序的α-螺旋，而残基1-5和29-35显示化学位移，其指示无规卷曲或β-折叠构象。BM 2-TM螺旋的长度类似于AM 2-TM，尽管它们的氨基酸序列显著不同。相比之下，大的N-15化学位移的差异之间观察到的双层结合的BM 2和胶束结合的BM 2，表明TM螺旋构象和骨架氢键在脂质双层不同于胶束结合的构象。此外，胶束结合的BM 2的H-N化学位移缺乏预期的卷曲螺旋的周期性趋势，这与胶束中存在的卷曲螺旋结构不一致。这些结果为确定四聚体BM 2的完整三维结构以阐明其质子传导机制奠定了基础。
Influenza A and B viruses cause seasonal flu epidemics. The M2 protein of influenza B (BM2) is a membrane-embedded tetrameric proton channel that is essential for the viral lifecycle. BM2 is a functional analog of AM2 but shares only 24% sequence identity for the transmembrane (TM) domain. The structure and function of AM2, which is targeted by two antiviral drugs, have been well characterized. In comparison, much less is known about the structure of BM2 and no drug is so far available to inhibit this protein. Here we use solid-state NMR spectroscopy to investigate the conformation of BM2(1-51) in phospholipid bilayers at high pH, which corresponds to the closed state of the channel. Using 2D and 3D correlation NMR experiments, we resolved and assigned the C-13 and N-15 chemical shifts of 29 residues of the TM domain, which yielded backbone (phi, psi) torsion angles. Residues 6-28 form a well-ordered alpha-helix, whereas residues 1-5 and 29-35 display chemical shifts that are indicative of random coil or beta-sheet conformations. The length of the BM2-TM helix resembles that of AM2-TM, despite their markedly different amino acid sequences. In comparison, large N-15 chemical shift differences are observed between bilayer-bound BM2 and micelle-bound BM2, indicating that the TM helix conformation and the backbone hydrogen bonding in lipid bilayers differ from the micelle-bound conformation. Moreover, H-N chemical shifts of micelle-bound BM2 lack the periodic trend expected for coiled coil helices, which disagree with the presence of a coiled coil structure in micelles. These results establish the basis for determining the full three-dimensional structure of the tetrameric BM2 to elucidate its proton-conduction mechanism.