SED超抗原MHCⅡ类分子结合位点的研究

Localization of MHC class Ⅱ binding sites on superantigen SED

目的 :运用定点突变技术确定SED超抗原的MHCⅡ结合位点。方法 :首先检测突变体的促T淋巴细胞增殖活性 ;用FITC标记SED ,对增殖活性降低的突变体 ,进一步用竞争结合实验检测其MHCⅡ结合活性。结果 :突变体SEDN2 3A、SEDN2 3A H2 6R和SEDF4 5A 的促增殖活性均显著降低 ,初步推测 2 3、2 6和 4 5位氨基酸可能参与了SED与MHC的相互作用。竞争结合实验证明F4 5位氨基酸是SED与MHCⅡ类分子结合的关键位点。结论 :F4 5位氨基酸是SED与MHCⅡ类分子结合的关键位点 ;2 3和 2 6位氨基酸可能参与了SED与T细胞受体 (TCR)Vβ的识别 。

Objective:To locate the MHC classⅡbinding sites on superantigen SED by site directed mutagenesis. Methods:The mitogen activity of mutants was firstly detected. Then, SED was marked with FITC. The mutants, of which mitogen activity decreased significantly, were detected their ability of binding to MHCⅡby competition assay.Results: The mitogen activity of mutant SEDN23A, SEDN23A/H26R and SEDF45A decreased significantly. Competition assay showed that F45 ,but not N23 and H26, was an important residue binding to MHCⅡ. Conclusion:F45 is a critical residue of SED binding to MHCⅡ. N23 and H26 are probably the active sites of SED interacting with TCRVβ.