一种从大肠杆菌包涵体中分离纯化GST-TRAF6融合蛋白的方法

Purification of GST-TRAF6 Fusion Proteins from Inculsion Body Expressed in E. coli

利用8 mol/L尿素溶液对表达在大肠杆菌包涵体中的GST-TRAF6融合蛋白进行变性,通过逐级稀释复性的方法对尿素溶解后的GST-TRAF6融合蛋白进行复性,将复性后的GST-TRAF6融合蛋白进一步利用谷胱甘肽琼脂糖树脂亲和层析的方法进行分离纯化,将分离纯化后的蛋白通过Western blot方法进行验证,最后利用体外泛素化反应检测经包涵体变性、复性和纯化后的GST-TRAF6融合蛋白的生物学活性。经过包涵体变性、梯度稀释复性和谷胱甘肽琼脂糖树脂亲和层析3个步骤后纯化得到纯度达90%以上、浓度为396 ng/μL的蛋白质溶液。利用GST蛋白作为对照,经Western blot验证表明,纯化得到的蛋白确为GSTTRAF6融合蛋白。进一步利用体外泛素化反应分析其泛素连接酶活性发现,17 ng/μL浓度的GST-TRAF6融合蛋白能够以泛素分子作为底物在5 min内快速催化自由泛素链的生成。结果表明,表达在大肠杆菌包涵体中的GST-TRAF6融合蛋白经尿素变性溶解后能够成功复性并分离纯化,在溶解性改变的同时恢复了其泛素连接酶活性。为从大肠杆菌包涵体中大规模分离纯化蛋白质提供了一种新的复性方法。

There was only a minor fraction of GST-TRAF6 fusion proteins were observed soluble when expressed in E.coli. Most of the GST-TRAF6 fusion proteins were present in the inclusion body, in which the expressed proteins aggregate and exist in inactive. To obtain GST-TRAF6 fusion protein in a high yield and high purity, a method to purify the GST-TRAF6 fusion proteins from inclusion body without any loss of its bioactivity was constructed. Firstly, the inclusion body was denatured with 8 mol/L urea. Secondly, the GST-TRAF6 fusion protein in inclusion body were gradually solubilized by gradient dilution renaturation. Once the GST-TRAF6 fusion protein was fully dissolved in renaturation solution, it was conventional to purify the GST-TRAF6 fusion protein with glutathione sepharose 4B. The specificity and the bioactivity of the purified GST-TRAF6 fusion protein were testified by western blot and in vitro ubiquitination assay, respectively. The results indicated that GST-TRAF6 fusion protein were successfully solubilized by gradient dilution renaturation following the denaturation of 8 mol/L urea, the concentration of the purified GST-TRAF6 fusion protein was achieved a concentration of 396 ng/μL with a purity over 90%. The specificity of this GST-TRAF6 fusion proteins were identified with anti-GST western blot. In vitro ubiquitination assay indicated that the GST-TRAF6 fusion protein in a concentration of 17 ng/μL could rapidly catalyze the formation of free ubiquitin chains within 5 minutes. In conclusion, it was found that the GST-TRAF6 fusion protein could be successfully renatured with the method of gradient dilution renaturation with the recovery of its capability of ubiquitin ligase. This results would supply a useful method for the large-scale purification of proteins from inclusion body when expressed in E. coli.