Receptor binding and priming of the spike protein of SARS-CoV-2 for membrane fusion
Receptor binding and priming of the spike protein of SARS-CoV-2 for membrane fusion
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DOI：
10.1038/s41586-020-2772-0
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发表时间：
2020-09-17
期刊：
影响因子：
64.8
通讯作者：
Gamblin, Steven J.
中科院分区：
文献类型：
--
作者：
Benton, Donald J.;Wrobel, Antoni G.;Gamblin, Steven J.
利用冷冻电镜观察了ACE 2与SARS-CoV-2刺突蛋白复合物的连续结合过程，揭示了SARS-CoV-2刺突蛋白与受体结合以及刺突蛋白激活膜融合的机制。SARS-CoV-2是由病毒与ACE 2细胞表面受体结合（1-4）引发的，随后病毒与细胞膜融合，将病毒基因组释放到细胞中。受体结合和膜融合活性均由病毒刺突糖蛋白介导（5-7）。与其他I类膜融合蛋白一样，刺突蛋白在切割后被切割，在这种情况下被弗林蛋白酶切割成在切割后保持结合的S1和S2组分（8-10）。受体结合后的融合激活被认为涉及第二个蛋白水解位点（S2 '）的暴露，其裂解是释放融合肽所必需的（11，12）。在这里，我们分析了结合ACE 2的弗林蛋白酶切割形式的SARS冠状病毒-2刺突蛋白使用冷冻电子显微镜。我们分类十种不同的分子种类，包括未结合的，封闭的穗三聚体，完全开放的ACE 2结合的三聚体和解离的单体S1结合ACE 2。这10个结构描述了ACE 2结合事件，这些事件使尖峰三聚体不稳定，逐渐打开，并从各个S1组件中取出。开放过程减少了S1的接触，并揭开了三聚体S2的核心，引发蛋白融合激活和ACE 2结合的S1单体的解离。这些结构还揭示了ACE 2结合后S1亚结构域的重折叠，其破坏了与S2的相互作用，这涉及Asp 614（13-15），并导致邻近二级（S2 '）切割位点的S2结构的不稳定。
Cryo-electron microscopy structures of consecutive binding events of ACE2 in complex with the spike protein of SARS-CoV-2 reveal the mechanisms of receptor binding by the spike protein and activation for membrane fusion by the spike protein of SARS-CoV-2.Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is initiated by virus binding to the ACE2 cell-surface receptors(1-4), followed by fusion of the virus and cell membranes to release the virus genome into the cell. Both receptor binding and membrane fusion activities are mediated by the virus spike glycoprotein(5-7). As with other class-I membrane-fusion proteins, the spike protein is post-translationally cleaved, in this case by furin, into the S1 and S2 components that remain associated after cleavage(8-10). Fusion activation after receptor binding is proposed to involve the exposure of a second proteolytic site (S2 '), cleavage of which is required for the release of the fusion peptide(11,12). Here we analyse the binding of ACE2 to the furin-cleaved form of the SARS-CoV-2 spike protein using cryo-electron microscopy. We classify ten different molecular species, including the unbound, closed spike trimer, the fully open ACE2-bound trimer and dissociated monomeric S1 bound to ACE2. The ten structures describe ACE2-binding events that destabilize the spike trimer, progressively opening up, and out, the individual S1 components. The opening process reduces S1 contacts and unshields the trimeric S2 core, priming the protein for fusion activation and dissociation of ACE2-bound S1 monomers. The structures also reveal refolding of an S1 subdomain after ACE2 binding that disrupts interactions with S2, which involves Asp614(13-15) and leads to the destabilization of the structure of S2 proximal to the secondary (S2 ') cleavage site.