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人白细胞介素—2(Interleukin 2,IL—2)含有3个半胱氨酸(Cys),其中第58位和第105位Cys形成二硫键,第125位Cys的巯基游离。应用PCR和定点突变技术将编码125位Cys的密码子突变成编码丙氨酸(Ala)的密码子,将此突变基因(hIL—2a)受控于P_RP_L串联启动子和人工合成SD序列,在E.coli中获得高效表达,用凝胶过滤法分离表达产物获得新型白细胞介素2[rIL—2(125-Ala)],其比活性达1×10~7IU/mg蛋白。
Human Interleukin 2 (IL-2) contains 3 cysteines (Cys), in which the 58th and 105th Cys form disulfide bonds, and the 125th Cys is free of sulfhydryl groups. The codon encoding Cys at position 125 was mutated to the codon encoding alanine (Ala) by PCR and site-directed mutagenesis. The mutant gene (hIL-2a) was controlled by the P_RP_L tandem promoter and the synthetic SD sequence. The recombinant protein IL-2 (rIL-2 (125-Ala)] was expressed in E.coli and its specific activity was 1 × 10-7IU / mg protein.