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目的:分析金黄色葡萄球菌肠毒素C2的T细胞受体结合区域α3结构中,第24位甲硫氨酸对其超抗原活性的影响作用。方法:应用定点突变技术对金黄色葡萄球菌肠毒素C2的Met24进行无意义突变,获得突变蛋白SEC2(M24A),对突变蛋白和野生型蛋白的体内、体外超抗原活性进行比较。结果:分别对野生型蛋白及突变蛋白的免疫刺激活性、肿瘤抑制活性、体内致热毒性进行了比较,发现突变蛋白的增值指数(PI)、抑瘤率、热源效应与野生型相比无显著差异(P>0.05),这表明对第24位甲硫氨酸的替换没有对金黄色葡萄球菌肠毒素C2的超抗原活性造成明显影响。结论:在金黄色葡萄球菌肠毒素C2的α3结构中,Met24并不是决定其超抗原活性的重要氨基酸残基。
Objective: To analyze the effect of methionine 24 on the superantigen activity of staphylococcal enterotoxin C2 in the α3 structure of T cell receptor binding domain. Methods: The site-directed mutagenesis was used to detect the Met24 of Staphylococcus aureus enterotoxin C2. The mutant protein SEC2 (M24A) was obtained and the in vivo and in vitro superantigen activity of the mutant protein and the wild type protein were compared. Results: The immunostimulatory activity, tumor inhibitory activity and in vivo pyrogenic toxicity of wild-type protein and mutein were compared respectively. There was no significant difference in proliferation index (PI), tumor inhibition rate and heat source effect between mutant and wild type (P> 0.05), suggesting that substitution of methionine 24 did not have a significant effect on the superantigen activity of Staphylococcal enterotoxin C2. Conclusion: Met24 is not an important amino acid residue that determines its superantigen activity in the α3 structure of Staphylococcal enterotoxin C2.