作为多才多艺的类寄生虫黄蜂,Leptopilina异质瘤在果蝇属的许多果蝇上都非常成功。寄生虫在其毒液中产生专门的多策略细胞外囊泡(EV)样结构。蛋白质组学分析确定了几种免疫相关蛋白,包括结蛋白肽,LhKNOT,含有结构保守的抑制剂半胱氨酸结(ICK)折叠,它存在于来自不同分类群的蛋白质中。我们对LhKNOT的36个残基核心结蛋白折叠的结构和对接分析显示,除了结蛋白基序本身,它还具有阳离子-极地-阳离子(CPC)剪辑。CPC夹基序被认为促进肝素结合蛋白中的抗微生物活性。令人惊讶的是,大多数测试的ICK也具有CPC剪辑图案,包括75种与LhKNOT具有高度序列和/或结构相似性的真正植物和节肢动物结蛋白。像LhKNOT和其他75种结蛋白一样,甚至果蝇Drosom霉素抗真菌肽,果蝇Toll-NF-κB免疫途径的典型靶基因,包含此CPC剪辑主题。一起,我们的结果表明寄生虫LhKNOT可能具有防御功能.CPC剪辑主题的流行,这里检查的结蛋白中半胱氨酸结的内在特征,表明所得的3D拓扑结构对于它们的生化功能很重要。CPC片段可能是在许多不同的蛋白质中发现的高度保守的结构基序,具有报道的肝素结合能力,包括淀粉样蛋白.打结素是治疗药物开发的目标,并深入了解它们的结构-功能关系将推动新药设计。
As generalist parasitoid wasps, Leptopilina heterotoma are highly successful on many species of fruit flies of the genus Drosophila. The parasitoids produce specialized multi-strategy extracellular vesicle (EV)-like structures in their venom. Proteomic analysis identified several immunity-associated proteins, including the knottin peptide, LhKNOT, containing the structurally conserved inhibitor cysteine knot (ICK) fold, which is present in proteins from diverse taxa. Our structural and docking analysis of LhKNOT\'s 36-residue core knottin fold revealed that in addition to the knottin motif itself, it also possesses a Cation-Polar-Cation (CPC) clip. The CPC clip motif is thought to facilitate antimicrobial activity in heparin-binding proteins. Surprisingly, a majority of ICKs tested also possess the CPC clip motif, including 75 bona fide plant and arthropod knottin proteins that share high sequence and/or structural similarity with LhKNOT. Like LhKNOT and these other 75 knottin proteins, even the Drosophila Drosomycin antifungal peptide, a canonical target gene of the fly\'s Toll-NF-kappa B immune pathway, contains this CPC clip motif. Together, our results suggest a possible defensive function for the parasitoid LhKNOT. The prevalence of the CPC clip motif, intrinsic to the cysteine knot within the knottin proteins examined here, suggests that the resultant 3D topology is important for their biochemical functions. The CPC clip is likely a highly conserved structural motif found in many diverse proteins with reported heparin binding capacity, including amyloid proteins. Knottins are targets for therapeutic drug development, and insights into their structure-function relationships will advance novel drug design.