Superantigen-immunoreceptor interactions

描述(由申请人提供)：建议研究的目标是 确定分子的三维结构和结合性质 细菌免疫调节剂--关节炎支原体来源的有丝分裂原 与人类类风湿性关节炎的发展有关的蛋白质。妈妈是一个 与主要组织相容性复合体(MHC)结合的可溶性26 kDa蛋白 II类分子，并激活大量携带特定T细胞的T细胞 细胞受体(TCR)Vβ链。在这方面，MAM的功能如下 传统的超抗原通过刺激强效超抗原而致病 非特异性免疫反应。然而，MAM并不共享显著序列 与其他超抗原同源性，与其他超抗原相反， MAM与TCR的结合受TCR的CDR3区域的影响。按顺序 为了更好地了解这种新型超抗原的生物学特性，以下是 具体目标将被追求：1)确定晶体结构 重组MAM(RMAM)；2)测定rMAM的亲和力和动力学参数 结合TCRβ链和MHC II类分子；3)确定晶体 RMAM与TCRβ链和MHC-II类分子络合时的结构 分子。RMAM和rMAM与TCRβ链络合的小晶体 已经被生产出来了。这项研究将解决三维 MAM的结构以及定义其与TCR和MHC II类的相互作用 分子。从长远来看，所获得的知识将为 通过这种独特的方式理解T细胞激活的分子基础 超抗原，用于确定其在触发和加重疾病中的作用 自身免疫性关节炎，以及开发基于结构的治疗方法 疾病。

DESCRIPTION (provided by applicant): The objective of the proposed research is to determine the three-dimensional structure and binding properties of Mycoplasma arthritidis-derived mitogen (MAM), a bacterial immunoregulatory protein implicated in the development of human rheumatoid arthritis. MAM is a soluble 26 kDa protein that binds to major histocompatibility complex (MHC) class II molecules and activates large numbers of T cells bearing particular T cell receptor (TCR) V beta chains. In this respect, MAM functions like conventional superantigens that cause disease by stimulating a strong nonspecific immune response. However, MAM does not share significant sequence homology with other superantigens and, in contrast to other superantigens, binding of MAM to the TCR is influenced by the CDR3 region of the TCR. In order to better understand the biology of this novel superantigen, the following specific aims will be pursued: 1) Determine the crystal structure of recombinant MAM (rMAM); 2) Determine the affmity and kinetic parameters of rMAM binding to TCR beta chains and MHC class II molecules; 3) Determine the crystal structures of rMAM when complexed with TCR beta chains and with MHC class II molecules. Small crystals of rMAM and of rMAM complexed with a TCR beta chain have already been produced. This study will resolve the three-dimensional structure of MAM as well as define its interaction with TCRs and MHC class II molecules. In the long term, the knowledge acquired will lay the groundwork for understanding the molecular basis of T cell activation by this unique superantigen, for determining its role in triggering and exacerbating autoimmune arthritis, and for developing structure-based therapies to treat disease.