Nervous necrosis virus (NNV) is a non-enveloped virus that causes massive mortality in aquaculture fish production worldwide. Recently X-ray crystallography and single particle cryo-EM have independently determined the icosahedral capsid of NNV to near-atomic resolutions to show the capsid protein is composed of a S-domain (shell) and a P-domain (protrusion) connected by a linker. However, the structure of the spike on NNV capsid made of trimeric P-domains was poorly resolved by cryo-EM. In addition, comparing the spike in the cryo-EM with that by X-ray suggests that the P-domain can move drastically relative to the shell, implicating an underlying structural mechanism during the infectious process. Yet, it remains unclear that such structural re-arrangement is ascribed to the change of the conformation of individual P-domain or in the association among P-domains. Given that molecular structure of the P-domain in solution phase is still lacking, we aim to determine the structure of the P-domain by solution NMR spectroscopy. In this communication, we report backbone and side chain ¹H, ¹³C and ¹⁵N chemical shifts of the P-domain (residues 221–338) together with the linker region (residues 214–220), revealing ten β-strands via chemical shift propensity analysis. Our findings are consistent with the X-ray crystal structure of the P-domain reported elsewhere. The current study provides a framework towards further structural analyses of the P-domain in various solution conditions.

中文翻译：

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龙石斑鱼神经坏死病毒衣壳蛋白突出结构域的NMR分配。

神经坏死病毒（NNV）是一种非包膜病毒，可导致全世界水产养殖鱼类生产中的大量死亡。最近，X射线晶体学和单晶冷冻EM技术已独立确定NNV的二十面体衣壳至接近原子分辨率，显示该衣壳蛋白由S结构域（壳）和P结构域（突出）组成，并通过链接器。然而，由冷冻EM难以分辨由三聚体P结构域制成的NNV衣壳上的尖峰的结构。此外，将冷冻EM的峰值与X射线的峰值进行比较表明，P结构域可以相对于外壳急剧移动，这暗示了在感染过程中潜在的结构机制。然而，仍不清楚这种结构的重新排列是由于单个P结构域的构象变化或P结构域之间的缔合变化所致。鉴于溶液相中P结构域的分子结构仍然缺乏，我们旨在通过溶液NMR光谱法确定P结构域的结构。在本次交流中，我们报告了骨干和侧链P结构域（残基221-338）与接头区域（残基214-220）的¹ H，¹³ C和¹⁵ N化学位移，通过化学位移倾向分析显示10条β链。我们的发现与其他地方报道的P结构域的X射线晶体结构一致。当前的研究为进一步解决各种条件下的P结构域结构提供了框架。