The microneme proteins EtMIC4 and EtMIC5 of Eimeria tenella form a novel, ultra-high molecular mass protein complex that binds target host cells
The microneme proteins EtMIC4 and EtMIC5 of Eimeria tenella form a novel, ultra-high molecular mass protein complex that binds target host cells
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DOI：
10.1074/jbc.m702407200
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发表时间：
2007-06-08
影响因子：
4.8
通讯作者：
Tomley, Fiona M.
中科院分区：
文献类型：
--
作者：
Periz, Javier;Gill, Andrew C.;Tomley, Fiona M.
柔嫩艾美耳球虫与顶复门的其他寄生原生动物一样，使用放线菌-肌球蛋白动力的“滑动体”复合物侵入宿主细胞，并需要从微线细胞器分泌粘附蛋白到寄生虫表面上。E. tenella包括EtMIC 4，一种在其胞外结构域中具有多个血小板反应蛋白I型结构域和钙结合表皮生长因子样结构域的跨膜蛋白，和EtMIC 5，一种由属于纤溶酶原-苹果-线虫超家族的11个串联重复结构域组成的可溶性蛋白。我们发现EtMIC 4和EtMIC 5相互作用形成一个寡聚的、分子量为100的蛋白质复合物。通过非变性技术从裂解的寄生虫中纯化复合物，并且化学计量显示为[EtMIC 4] 2：[EtMIC 5] 1，EtMIC 4的八聚体非共价结合到EtMIC 5的四聚体。该复合物在寄生虫分泌途径内形成，并在分泌到寄生虫表面后维持。纯化的复合物与培养物中的许多上皮细胞系结合。这种复合物的鉴定和表征有助于全面了解多分子蛋白质复合物在感染期间病原体与其宿主之间的特异性相互作用中的作用。
Eimeria tenella, in common with other parasitic protozoa of the phylum Apicomplexa, invades host cells using an actino-myosin-powered "glideosome" complex and requires the secretion of adhesive proteins from the microneme organelles onto the parasite surface. Microneme proteins of E. tenella include EtMIC4, a transmembrane protein that has multiple thrombospondin type I domains and calcium-binding epidermal growth factor-like domains in its extracellular domain, and EtMIC5, a soluble protein composed of 11 tandemly repeated domains that belong to the plasminogen-apple-nematode superfamily. Weshow here that EtMIC4 and EtMIC5 interact to form an oligomeric, ultrahigh molecular mass protein complex. The complex was purified from lysed parasites by non-denaturing techniques, and the stoichiometry was shown to be [EtMIC4] 2:[EtMIC5] 1, with an octamer of EtMIC4 bound noncovalently to a tetramer of EtMIC5. The complex is formed within the parasite secretory pathway and is maintained after secretion onto the surface of the parasite. The purified complex binds to a number of epithelial cell lines in culture. Identification and characterization of this complex contributes to an overall understanding of the role of multimolecular protein complexes in specific interactions between pathogens and their hosts during infection.