The Unique Transmembrane Hairpin of Flavivirus Fusion Protein E Is Essential for Membrane Fusion
The Unique Transmembrane Hairpin of Flavivirus Fusion Protein E Is Essential for Membrane Fusion
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DOI：
10.1128/jvi.02458-10
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发表时间：
2011-05-01
影响因子：
5.4
通讯作者：
Stiasny, Karin
中科院分区：
文献类型：
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作者：
Fritz, Richard;Blazevic, Janja;Stiasny, Karin
被包裹的病毒与细胞膜的融合是由锚定在病毒脂双层中的蛋白质介导的，这些蛋白质能够触发推动融合所需的构象变化。黄病毒囊膜蛋白E是已知的唯一具有双膜锚定的病毒融合蛋白，由两个反平行的跨膜螺旋(TM1和TM2)组成。在多蛋白加工过程中，TM1作为第一个非结构蛋白的停止转移序列，TM2作为内部信号序列。到目前为止，这种特殊的C-末端螺旋发夹在膜融合中的可能作用还没有被研究过。我们通过研究森林脑炎病毒(TBEV)重组亚病毒颗粒(RSPs)的TM突变体来解决这个问题，RSPs是一个已建立的黄病毒膜融合的模型系统。工程突变包括TM2的缺失，两个TM结构域(TMD)都被相关的乙型脑炎病毒(JEV)取代，以及使用嵌合的TBEV-JEV膜锚。使用这些突变的RSP，我们提供了证据，表明TM2不仅是多蛋白加工的残留物，而且与TM1一起，在融合中发挥积极作用。TM的突变，包括TM2的缺失，都没有影响融合过程的早期步骤，但TM的相互作用显然有助于融合后E三聚体的稳定性和膜的完成合并。我们的数据为E的TMDs介导的内聚体和三聚体间相互作用提供了证据，从而扩展了现有的黄病毒膜融合模型。
The fusion of enveloped viruses with cellular membranes is mediated by proteins that are anchored in the lipid bilayer of the virus and capable of triggered conformational changes necessary for driving fusion. The flavivirus envelope protein E is the only known viral fusion protein with a double membrane anchor, consisting of two antiparallel transmembrane helices (TM1 and TM2). TM1 functions as a stop-transfer sequence and TM2 as an internal signal sequence for the first nonstructural protein during polyprotein processing. The possible role of this peculiar C-terminal helical hairpin in membrane fusion has not been investigated so far. We addressed this question by studying TM mutants of tick-borne encephalitis virus (TBEV) recombinant subviral particles (RSPs), an established model system for flavivirus membrane fusion. The engineered mutations included the deletion of TM2, the replacement of both TM domains (TMDs) by those of the related Japanese encephalitis virus (JEV), and the use of chimeric TBEV-JEV membrane anchors. Using these mutant RSPs, we provide evidence that TM2 is not just a remnant of polyprotein processing but, together with TM1, plays an active role in fusion. None of the TM mutations, including the deletion of TM2, affected early steps of the fusion process, but TM interactions apparently contribute to the stability of the postfusion E trimer and the completion of the merger of the membranes. Our data provide evidence for both intratrimer and intertrimer interactions mediated by the TMDs of E and thus extend the existing models of flavivirus membrane fusion.