Huynh My-Hang, Liu Bing, Henry Maud, Liew Lloyd, Matthews Stephen J, Carruthers Vern B
From the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109 and.
the Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
J Biol Chem. 2015 Jan 16;290(3):1432-41. doi: 10.1074/jbc.M114.613646. Epub 2014 Nov 19.
Toxoplasma gondii parasites must actively invade host cells to propagate. Secretory microneme proteins have been shown to be important for both gliding motility and active invasion. MIC2-M2AP is a protein complex that is essential for productive motility and rapid invasion by binding to host cell surface receptors. To investigate the architecture of the MIC2 and M2AP complex, we identified the minimal domains sufficient for interaction and solved the NMR solution structure of the globular domain of M2AP. We found that M2AP adopts a modified galectin fold similar to the C-terminal domain of another microneme protein, MIC1. NMR and immunoprecipitation analyses implicated hydrophobic residues on one face of the M2AP galectin fold in binding to the membrane proximal sixth thrombospondin type I repeat domain of MIC2. Our findings provide a second example of a galectin fold adapted for microneme protein-protein interactions and suggest a conserved strategy for the assembly and folding of diverse protein complexes.
弓形虫寄生虫必须主动侵入宿主细胞才能繁殖。分泌性微线体蛋白已被证明对滑行运动和主动侵入都很重要。MIC2-M2AP是一种蛋白质复合物，通过与宿主细胞表面受体结合，对有效的运动性和快速侵入至关重要。为了研究MIC2和M2AP复合物的结构，我们确定了足以进行相互作用的最小结构域，并解析了M2AP球状结构域的核磁共振溶液结构。我们发现M2AP采用了一种修饰的半乳糖凝集素折叠结构，类似于另一种微线体蛋白MIC1的C末端结构域。核磁共振和免疫沉淀分析表明，M2AP半乳糖凝集素折叠结构一侧的疏水残基与MIC2的膜近端第六个血小板反应蛋白I型重复结构域结合。我们的研究结果提供了第二个适用于微线体蛋白-蛋白质相互作用的半乳糖凝集素折叠结构的例子，并提出了一种用于组装和折叠不同蛋白质复合物的保守策略。
