The solution structure of SARS-CoV-2 nonstructural protein 7 (nsp7) at pH 7.0 has been determined by NMR spectroscopy. nsp7 is conserved in the coronavirinae subfamily and is an essential co-factor of the viral RNA-dependent RNA polymerase for active and processive replication. Similar to the previously deposited structures of SARS-CoV-1 nsp7 at acidic and basic conditions, SARS-CoV-2 nsp7 has a helical bundle folding at neutral pH. Remarkably, the α4 helix shows gradual dislocation from the core α2-α3 structure as pH increases from 6.5 to 7.5. The protonation state of residue H36 contributes to the change of nsp7’s intramolecular interactions, and thus, to the structural variation near-neutral pH. Spin-relaxation results revealed that all three loop regions in nsp7 possess dynamic properties associated with this structural variation.

中文翻译：

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SARS-CoV-2 nsp7结构的pH依赖性多态性

SARS-CoV-2 非结构蛋白 7 (nsp7) 在 pH 7.0 时的溶液结构已通过核磁共振光谱确定。nsp7 在冠状病毒亚科中是保守的亚家族，并且是病毒 RNA 依赖性 RNA 聚合酶的重要辅助因子，用于主动和持续复制。与先前在酸性和碱性条件下沉积的 SARS-CoV-1 nsp7 结构相似，SARS-CoV-2 nsp7 在中性 pH 下具有螺旋束折叠。值得注意的是，随着 pH 从 6.5 增加到 7.5，α4 螺旋显示出与核心 α2-α3 结构逐渐错位。残基 H36 的质子化状态有助于改变 nsp7 的分子内相互作用，从而导致接近中性 pH 值的结构变化。自旋弛豫结果表明，nsp7 中的所有三个环区域都具有与这种结构变化相关的动态特性。