牛肠激酶轻链在大肠杆菌中的非融合表达及生物学活性分析

Non-Fusional Expression of Bovine Enterokinase Light Chain in Escherichia Coli and its Bioactivity Analysis

该研究尝试利用大肠杆菌表达体系以非融合蛋白形式表达牛肠激酶轻链(EK_(LC))。利用基因重组技术构建重组表达载体p6×His-D_4K-EK_(LC)并转化至E. coli DH5α,37℃过夜培养,超声破壁法释放菌体蛋白并收集包涵体,考察包涵体在不同浓度下的复性效率。复性后的目的蛋白经金属离子亲和层析纯化,并以EK_(LC)自切方式移除重组EK_(LC)的N-端6×His-D_4K序列得到具有天然N-端氨基酸序列的EK_(LC),酶活性测定结果显示该研究所制备的重组EK_(LC)高于商品化牛肠激酶。重组EK_(LC)在大肠杆菌中非融合表达成功,为实现EK_(LC)的经济、高效制备研究奠定了实验基础。

In this study,the author attempt to express bovine enterokinase light chain(EKLC)without fusion partner in E.coli system.The DNA sequence of EKLCcontaining 6×His-D4K DNA at its 5’end,was synthesized using a chemical method,and then sub-cloned into the Bam HI/HindⅢsite of p Green-S plasmid by employing gene recombination technology,yielding the vector p6×His-D4K-EKLCfor producing the recombinant 6×His-D4K-EKLC.The cells E.coli DH5αharboring p6×His-D4K-EKLC were cultured at 37℃for overnight,then the cells were harvested by centrifugation,and the bacterial protein was released by ultrasonic wall breaking method and inclusion bodies were collected and analyzed by SDS-PAGE.Then,the inclusion bodies were endured protein renaturation procedure.The renaturation efficiency of inclusion bodies at different concentrations was also investigated.After renaturation,the target protein was purified by IMAC,and the natural N-terminal amino acid sequence of EKLCwas exposed via autocatalytic cleavage reaction.The enzyme activity was determined by using Gly-(Asp)4-Lys-β-naphthylamide as a substrate.The result of double restriction enzyme digestion showed that the recombinant vector was constructed correctly.SDS-PAGE assay showed that the product was mainly inclusion body,and in the author’s renaturation procedure,the inclusion bodies were successfully refold at high concentration.The target protein was successfully purified by IMAC.After autocatalytic cleavage reaction,the 6×His-D4K sequence was removed and exposed the natural N-terminal amino acid sequence of EKLC.And the results of enzyme bioactivity analysis showed that the EKLCprepared in this study was 1.5 fold of the commercial one at A580 nm.The successful expression of EKLCin E.coli provided an experimental foundation for the economic and efficient preparation of EKLCin future.