Borloo Jimmy, Geldhof Peter, Peelaers Iris, Van Meulder Frederik, Ameloot Paul, Callewaert Nico, Vercruysse Jozef, Claerebout Edwin, Strelkov Sergei V, Weeks Stephen D
Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
Acta Crystallogr D Biol Crystallogr. 2013 Apr;69(Pt 4):493-503. doi: 10.1107/S0907444912050019. Epub 2013 Mar 9.
The cysteine-rich secretory/antigen 5/pathogenesis-related 1 (CAP) protein superfamily is composed of a functionally diverse group of members that are found in both eukaryotes and prokaryotes. The excretome/secretome of numerous helminths (parasitic nematodes) contains abundant amounts of CAP members termed activation-associated secreted proteins (ASPs). Although ASPs are necessary for the parasitic life cycle in the host, the current lack of structural and functional information limits both understanding of their actual role in host-parasite interactions and the development of new routes in controlling parasitic infections and diseases. Alleviating this knowledge gap, a 1.85 Å resolution structure of recombinantly produced Oo-ASP-1 from Ostertagia ostertagi, which is one of the most prevalent gastrointestinal parasites in cattle worldwide, was solved. Overall, Oo-ASP-1 displays the common hallmark architecture shared by all CAP-superfamily members, including the N-terminal CAP and C-terminal cysteine-rich domains, but it also reveals a number of highly peculiar features. In agreement with studies of the natively produced protein, the crystal structure shows that Oo-ASP-1 forms a stable dimer that has been found to be primarily maintained via an intermolecular disulfide bridge, hence the small interaction surface of only 306.8 Å(2). Moreover, unlike any other ASP described to date, an additional intramolecular disulfide bridge links the N- and C-termini of each monomer, thereby yielding a quasi-cyclic molecule. Taken together, the insights presented here form an initial step towards a better understanding of the actual biological role(s) that this ASP plays in host-parasite interactions. The structure is also essential to help to define the key regions of the protein suitable for development of ASP-based vaccines, which would enable the current issues surrounding anthelmintic resistance in the treatment of parasitic infections and diseases to be circumvented.
富含半胱氨酸的分泌型/抗原5/病程相关蛋白1（CAP）超家族由功能多样的成员组成，这些成员在真核生物和原核生物中均有发现。许多蠕虫（寄生线虫）的分泌组/分泌蛋白组中含有大量被称为激活相关分泌蛋白（ASP）的CAP成员。虽然ASP对于寄生虫在宿主体内的生命周期是必需的，但目前缺乏结构和功能信息，这限制了我们对其在宿主-寄生虫相互作用中实际作用的理解，也限制了控制寄生虫感染和疾病新途径的开发。为了填补这一知识空白，我们解析了重组表达的牛奥斯特他线虫Oo-ASP-1的结构，其分辨率为1.85 Å，牛奥斯特他线虫是全球牛群中最常见的胃肠道寄生虫之一。总体而言，Oo-ASP-1呈现出所有CAP超家族成员共有的标志性结构，包括N端的CAP结构域和C端富含半胱氨酸的结构域，但它也展现出许多非常独特的特征。与对天然产生的该蛋白的研究一致，晶体结构表明Oo-ASP-1形成了一个稳定的二聚体，该二聚体主要通过分子间二硫键维持，因此其相互作用表面较小，仅为306.8 Ų。此外，与迄今为止描述的任何其他ASP不同，一个额外的分子内二硫键连接了每个单体的N端和C端，从而形成了一个准环状分子。综上所述，本文所提供的见解是朝着更好地理解这种ASP在宿主-寄生虫相互作用中实际生物学作用迈出的第一步。该结构对于帮助确定适合开发基于ASP的疫苗的蛋白关键区域也至关重要，这将能够规避目前在治疗寄生虫感染和疾病中围绕驱虫抗性的问题。
