Structural basis for the enhancement of virulence by viral spindles and their in vivo crystallization
Structural basis for the enhancement of virulence by viral spindles and their in vivo crystallization
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DOI：
10.1073/pnas.1418798112
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发表时间：
2015-03-31
影响因子：
11.1
通讯作者：
Coulibaly, Fasseli
中科院分区：
文献类型：
--
作者：
Chiu, Elaine;Hijnen, Marcel;Coulibaly, Fasseli
化学农药给农业带来的巨大好处被对非目标物种的广泛环境破坏和对人类健康的威胁部分抵消。微生物生物杀虫剂被认为是安全和高度特异性的替代品，但通常缺乏效力。由昆虫痘病毒产生的孢子是fusolin蛋白的晶体，其不仅显著增强这些病毒的毒力，而且在共饲养实验中，还增强不相关病原体的杀虫活性。然而，纺锤体组装成超稳定晶体并增强毒力的机制尚不清楚。在这里，我们描述的病毒纺锤体的结构确定的X-射线显微晶体学从体内晶体纯化从受感染的昆虫。我们发现fusolin的C-末端分子臂介导球状结构域的组装，其具有几丁质噬菌的溶解性多糖单加氧酶的特征。解释其独特的稳定性，fusolin二聚体之间的二硫键的3D网络共价交联纺锤体的整个晶体基质。然而，在被新宿主摄取后，分子臂的去除废除了这种稳定网络，导致纺锤体的溶解。然后释放的单加氧酶结构域自由地破坏保护昆虫免受口腔感染的富含几丁质的围食基质。这里揭示的作用模式可以指导设计有效的纺锤体作为生物杀虫剂的协同添加剂。
The great benefits that chemical pesticides have brought to agriculture are partly offset by widespread environmental damage to nontarget species and threats to human health. Microbial bioinsecticides are considered safe and highly specific alternatives but generally lack potency. Spindles produced by insect poxviruses are crystals of the fusolin protein that considerably boost not only the virulence of these viruses but also, in cofeeding experiments, the insecticidal activity of unrelated pathogens. However, the mechanisms by which spindles assemble into ultra-stable crystals and enhance virulence are unknown. Here we describe the structure of viral spindles determined by X-ray microcrystallography from in vivo crystals purified from infected insects. We found that a C-terminal molecular arm of fusolin mediates the assembly of a globular domain, which has the hallmarks of lytic polysaccharide monooxy-genases of chitinovorous bacteria. Explaining their unique stability, a 3D network of disulfide bonds between fusolin dimers covalently crosslinks the entire crystalline matrix of spindles. However, upon ingestion by a new host, removal of the molecular arm abolishes this stabilizing network leading to the dissolution of spindles. The released monooxygenase domain is then free to disrupt the chitin-rich peritrophic matrix that protects insects against oral infections. The mode of action revealed here may guide the design of potent spindles as synergetic additives to bioinsecticides.