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对裂解事件的蛋白质组学分析揭示了一种关键寄生虫粘附复合物蛋白水解的动态两步机制。

Proteomic analysis of cleavage events reveals a dynamic two-step mechanism for proteolysis of a key parasite adhesive complex.

作者信息

Zhou Xing W, Blackman Michael J, Howell Steven A, Carruthers Vern B

机构信息

W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.

出版信息

Mol Cell Proteomics. 2004 Jun;3(6):565-76. doi: 10.1074/mcp.M300123-MCP200. Epub 2004 Feb 24.

Abstract

The transmembrane micronemal protein MIC2 and its partner M2AP comprise an adhesive complex that is required for rapid invasion of host cells by the obligate intracellular parasite Toxoplasma gondii. Recent studies have shown that the MIC2/M2AP complex undergoes extensive proteolytic processing on the parasite surface during invasion, including primary processing of M2AP by unknown proteases and proteolytic shedding of the complex by an anonymous protease called MPP1. While it was shown that MPP1-mediated cleavage is necessary for efficient invasion, it remained unclear whether the adhesive complex was liberated by juxtamembrane or intramembrane proteolysis. Here, using a three-phase strategy of assigning cleavage sites based on intact matrix-assisted laser desorption/ionization mass followed by confirmation by enzymatic digestion and inhibitor profiling, we demonstrate that M2AP is processed by two parasite-derived proteases called MPP2 and MPP3. We also define the substrate repertoire of MPP2 by two-dimensional differential gel electrophoresis using fluorescent tags. Finally, we use complementary mass spectrometric techniques to unequivocally show that MIC2 is shed by intramembrane cleavage within its anchoring domain. Based on the properties of this cleavage site, we conclude that the sheddase, MPP1, is likely a multipass membrane protease of the Rhomboid family. Our data support a novel two-step proteolysis model that includes primary processing of the MIC2/M2AP complex followed by secondary cleavage to shed the complex from the parasite surface during the final steps of invasion.

摘要

跨膜微线体蛋白MIC2及其伴侣M2AP构成一种粘附复合物,专性细胞内寄生虫刚地弓形虫快速侵入宿主细胞需要该复合物。最近的研究表明,MIC2/M2AP复合物在入侵过程中在寄生虫表面经历广泛的蛋白水解加工,包括未知蛋白酶对M2AP的初级加工以及一种名为MPP1的无名蛋白酶对该复合物的蛋白水解脱落。虽然已表明MPP1介导的切割对于有效入侵是必要的,但粘附复合物是通过近膜蛋白水解还是膜内蛋白水解释放仍不清楚。在这里,我们采用了一种三相策略,即基于完整的基质辅助激光解吸/电离质谱确定切割位点,随后通过酶切消化和抑制剂分析进行确认,结果表明M2AP由两种寄生虫来源的蛋白酶MPP2和MPP3加工。我们还通过使用荧光标签的二维差异凝胶电泳确定了MPP2的底物谱。最后,我们使用互补质谱技术明确表明MIC2在其锚定结构域内通过膜内切割而脱落。基于该切割位点的特性,我们得出结论,脱落酶MPP1可能是菱形家族的多跨膜蛋白酶。我们的数据支持一种新的两步蛋白水解模型,该模型包括MIC2/M2AP复合物的初级加工,随后在入侵的最后阶段进行二次切割,以使该复合物从寄生虫表面脱落。

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