GST-SOD1-R9融合蛋白的表达、纯化、稳定性与跨膜效应

Expression, purification, stability and transduction efficiency of GST-SOD1-R9 fusion protein

摘要:

穿膜肽TAT介导的双效抗氧化酶GST (谷胱甘肽巯基转移酶)-TAT-SOD1 (Cu, Zn 超氧化物歧化酶)，可有效清除胞内自由基，其预防氧化损伤的效果强于SOD1-TAT，但前者的跨膜能力不如后者。为增强双效抗氧化酶的跨膜效率，本研究融合了SOD1和穿膜肽R9，合成SOD1-R9全基因序列，并将其插入带有GST的原核表达载体pGEX-4T-1中，成功构建了GST-SOD1-R9融合蛋白表达质粒。然后，将重组质粒pGEX-4T-1-SOD1-R9转化大肠杆菌BL21 (DE3)，用IPTG诱导表达融合蛋白，通过改变诱导温度和诱导时间，确定了融合蛋白在25 ℃下表达11 h，可得到高表达量的可溶性GST-SOD1-R9融合蛋白。利用80%硫酸铵沉淀和GST琼脂糖珠纯化得到纯蛋白，应用SDS-PAGE和酶活性鉴定纯化的蛋白为正确表达的目标蛋白。GST-SOD1-R9融合蛋白的温度和pH稳定性实验结果证实，该蛋白在生理条件下具有良好的SOD和GST活性。细胞跨膜实验结果证明其跨膜能力与GST-TAT-SOD1融合蛋白相比显著增强 (P<0.05)。这些工作为深入研究GST-SOD1-R9的抗氧化损伤效应建立了基础。

Abstract:

The fusion of cell permeable peptide TAT and bifunctional antioxidant enzymes, GST (Glutathione sulfur transferase)-TAT-SOD1 (Cu, Zn superoxide dismutase), is an intracellular superoxide scavenger. Compared with SOD1-TAT, GST-TAT-SOD1 has better protective effect on oxidative damage but less transduction efficiency. A novel cell permeable bifunctional antioxidant enzymes with the fusion of GST, SOD1 and polyarginine R9 was constructed for higher transduction efficiency. The full nucleotide sequence of SOD1-R9 was synthesized and inserted into the prokaryotic expression vector pGEX-4T-1 with the GST tag. After the successful construction of the prokaryotic expression vectors of GST-SOD1-R9, the recombinant vector was then transformed into Escherichia coli BL21 (DE3) and the GST-SOD1-R9 fusion protein was produced with the induction of IPTG. The soluble expression of GST-SOD1-R9 fusion protein was combining with the induction temperature and time. The best soluble expression was obtained with the induction temperature of 25 ℃ and the induction time of 11 h. The fusion protein was purified through the combination of 80% ammonium sulfate precipitation and affinity chromatography using glutathione agarose, and verified by SDS-PAGE and special enzymatic activity. The thermal and pH stability of GST-SOD1-R9 fusion protein were analyzed and the SOD and GST activity of fusion protein were proved to be well maintained under physiological conditions. Finally, the transduction efficiency of GST-SOD1-R9 fusion protein was proved to be better than GST-TAT-SOD1 fusion protein (P<0.05). These works establish a foundation for further study of the protective effect of GST-SOD1-R9 fusion protein against oxidative damage.