White spot syndrome virus (WSSV) is the most virulent pathogen causing high mortality and economic loss in shrimp aquaculture and various crustaceans. Therefore, the understanding of molecular mechanisms of WSSV infection is important to develop effective therapeutics to control the spread of this viral disease. In a previous study, we found that VP37 could bind with shrimp haemocytes through the interaction between its C-terminal domain and heparin-like molecules on the shrimp cells, and this interaction can also be inhibited by sulphated galactan. In this study, we present the crystal structure of C-terminal domain of VP37 from WSSV at a resolution of 2.51 Å. The crystal structure contains an eight-stranded β-barrel fold with an antiparallel arrangement and reveals a trimeric assembly. Moreover, there are two sulphate binding sites found in the position corresponding to R213 and K257. In order to determine whether these sulphate binding sites are involved in binding of VP37 to heparin, mutagenesis was performed to replace these residues with alanine (R213A and K257A), and the Surface Plasmon Resonance (SPR) system was used to study the interaction of each mutated VP37 with heparin. The results showed that mutants R213A and K257A exhibited a significant loss in heparin binding activity. These findings indicated that the sites of R213 and K257 on the C-terminal domain of envelope protein VP37 are essential for binding to sulphate molecules of heparin. This study provides further insight into the structure of C-terminal domain of VP37 and it is anticipated that the structure of VP37 might be used as a guideline for development of antivirus agent targeting on the VP37 protein.

中文翻译：

---

白斑综合征病毒包膜蛋白 VP37 C 端结构域的晶体结构揭示了负责肝素结合的硫酸盐结合位点

白斑综合征病毒（WSSV）是导致对虾养殖和各种甲壳类动物高死亡率和经济损失的最毒的病原体。因此，了解 WSSV 感染的分子机制对于开发有效的治疗方法来控制这种病毒性疾病的传播非常重要。在之前的一项研究中，我们发现 VP37 可以通过其 C 端结构域与虾细胞上的肝素样分子之间的相互作用与虾血细胞结合，这种相互作用也可以被硫酸化半乳聚糖抑制。在这项研究中，我们以 2.51 Å 的分辨率展示了来自 WSSV 的 VP37 C 端结构域的晶体结构。晶体结构包含具有反平行排列的八股 β 桶状折叠，并显示出三聚体组装。而且，在对应于 R213 和 K257 的位置发现了两个硫酸盐结合位点。为了确定这些硫酸盐结合位点是否参与了 ​​VP37 与肝素的结合，进行了诱变以用丙氨酸（R213A 和 K257A）替换这些残基，并使用表面等离子体共振 (SPR) 系统来研究每个用肝素突变VP37。结果显示突变体R213A和K257A表现出肝素结合活性的显着丧失。这些发现表明，包膜蛋白 VP37 的 C 端结构域上的 R213 和 K257 位点对于与肝素硫酸盐分子的结合是必不可少的。