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Polar Networks Mediate Ion Conduction of the SARS-CoV-2 Envelope Protein
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-12-27 , DOI: 10.1021/jacs.4c13229
João Medeiros-Silva, Yanina Pankratova, Iva Sučec, Aurelio J. Dregni, Mei Hong

The SARS-CoV-2 E protein conducts cations across the cell membrane to cause pathogenicity to infected cells. The high-resolution structures of the E transmembrane domain (ETM) in the closed state at neutral pH and in the open state at acidic pH have been determined. However, the ion conduction mechanism remains elusive. Here, we use solid-state NMR spectroscopy to investigate the side chain structure, dynamics, and interactions of five polar residues at the N-terminal entrance of the channel and three polar residues at the C-terminal end. The chemical shifts of the N-terminal Glu8 reveal that the Glu side chain interacts with protons, Ca2+ and two neighboring Thr residues, and adopts distinct motionally averaged conformational ensembles. These polar interactions are sensitive to the presence of negatively charged lipids in the membrane. A T9I mutation, prevalent in the Omicron variants of SARS-CoV-2 E, perturbs these interactions and partially immobilizes the N-terminal segment. Deeper into the channel, two polar residues, Asn15 and Ser16, form interhelical hydrogen bonds in the closed state but become separated by water molecules in the open state. This is manifested by Asn15-Ser16 correlation signals at neutral pH and the loss of these correlations and the appearance of water cross peaks with Ser16 at acidic pH in the presence of Ca2+. Finally, the guanidinium side chain of the C-terminal Arg38 undergoes fast reorientations in the closed state but becomes more restricted in the open state. These results provide evidence for a dynamic and hydrogen-bonded N-terminal polar network that recruits and relays protons and Ca2+ in a lipid-dependent manner. Once inside, the ions permeate past the hydrophobic middle of the transmembrane domain with the help of enhanced hydrophilicity of the C-terminal channel lumen due to the insertion of the Arg38 side chain into the pore.

中文翻译:


Polar Networks 介导 SARS-CoV-2 包膜蛋白的离子传导



SARS-CoV-2 E 蛋白将阳离子传导穿过细胞膜,对受感染细胞造成致病性。已经确定了 E 跨膜结构域 (ETM) 在中性 pH 下关闭状态和在酸性 pH 下开放状态下的高分辨率结构。然而,离子传导机制仍然难以捉摸。在这里,我们使用固体 NMR 波谱来研究通道 N 端入口处的 5 个极性残基和 C 端的 3 个极性残基的侧链结构、动力学和相互作用。N 末端 Glu8 的化学位移表明 Glu 侧链与质子、Ca2+ 和两个相邻的 Thr 残基相互作用,并采用不同的运动平均构象集合。这些极性相互作用对膜中带负电荷的脂质的存在很敏感。SARS-CoV-2 E 的 Omicron 变体中普遍存在的 T9I 突变会扰乱这些相互作用并部分固定 N 端片段。在通道的更深处,两个极性残基 Asn15 和 Ser16 在闭合状态下形成螺旋间氢键,但在开通状态下被水分子分离。这表现为中性 pH 下的 Asn15-Ser16 相关信号,这些相关性的丧失以及在 Ca2+ 存在下酸性 pH 下与 Ser16 交叉峰的出现。最后,C 端 Arg38 的胍侧链在闭合状态下经历快速重新定向,但在开路状态下变得更加受限。这些结果为动态的氢键 N 末端极性网络提供了证据,该网络以脂质依赖性方式募集和传递质子和 Ca2+。 一旦进入,离子就会渗透到跨膜结构域的疏水中间,由于 Arg38 侧链插入孔中,C 末端通道腔的亲水性增强。
更新日期:2024-12-27
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