COVID-19, the infectious disease caused by the most recently discovered coronavirus SARS- CoV-2, has caused millions of sick people and thousands of deaths all over the world. The viral positive-sense single-stranded RNA encodes 31 proteins among which the spike (S) is undoubtedly the best known. Recently, protein E has been reputed as a potential pharmacological target as well. It is essential for the assembly and release of the virions in the cell. Literature describes protein E as a voltage-dependent channel with preference towards monovalent cations whose intracellular expression, though, alters Ca2+ homeostasis and promotes the activation of the proinflammatory cascades. Due to the extremely high sequence identity of SARS-CoV-2 protein E (E-2) with the previously characterized E-1 (i.e., protein E from SARS-CoV) many data obtained for E-1 were simply adapted to the other. Recent solid state NMR structure revealed that the transmembrane domain (TMD) of E-2 self-assembles into a homo-pentamer, albeit the oligomeric status has not been validated with the full-length protein. Prompted by the lack of a common agreement on the proper structural and functional features of E-2, we investigated the specific mechanism/s of pore-gating and the detailed molecular structure of the most cryptic protein of SARS-CoV-2 by means of MD simulations of the E-2 structure and by expressing, refolding and analyzing the electrophysiological activity of the transmembrane moiety of the protein E-2, in its full length. Our results show a clear agreement between experimental and predictive studies and foresee a mechanism of activity based on Ca2+ affinity.

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SARS-CoV-2 病毒蛋白 E 的电生理特性和结构预测

COVID-19 是由最近发现的冠状病毒 SARS-CoV-2 引起的传染病，已在全世界造成数百万人患病和数千人死亡。病毒的正链单链RNA编码31种蛋白质，其中刺突（S）无疑是最著名的。最近，蛋白质 E 也被认为是一个潜在的药理学靶点。它对于细胞中病毒粒子的组装和释放至关重要。文献将蛋白 E 描述为电压依赖性通道，优先选择单价阳离子，但其细胞内表达会改变 Ca2+稳态并促进促炎级联的激活。由于 SARS-CoV-2 蛋白 E (E-2) 与之前表征的 E-1（即来自 SARS-CoV 的蛋白 E）具有极高的序列同一性，为 E-1 获得的许多数据都简单地适用于其他数据。最近的固态核磁共振结构表明，E-2 的跨膜结构域 (TMD) 自组装成同源五聚体，尽管寡聚状态尚未用全长蛋白质进行验证。由于对 E-2 的正确结构和功能特征缺乏共识，我们通过以下方法研究了孔门控的具体机制以及 SARS-CoV-2 最神秘的蛋白质的详细分子结构：对 E-2 结构进行 MD 模拟，并通过表达、重折叠和分析全长蛋白质 E-2 跨膜部分的电生理活性。我们的结果显示实验和预测研究之间存在明显的一致性，并预见了基于 Ca 的活性机制2+亲和力。