芽孢杆菌β-折叠桶植酸酶的原核可溶性表达优化及包涵体复性研究

Optimizing Soluble Expression and Inclusion Body Renature Research of β-Propeller Phytase of Bacillus sp.HJB17 in E.coli

目的:来源于芽孢杆菌的β-折叠桶植酸酶基因PhyH,截去N端120个碱基编码的40个氨基酸后,成功构建了原核表达体系,通过两种方法分别得到有活性的目的蛋白PhyHT,并通过进一步纯化提高目的蛋白的纯度。方法:通过分子伴侣共表达系统提高目的蛋白的可溶性表达,并通过包涵体复性研究,从包涵体中制备出有活性的目的蛋白。结果:(1)目的蛋白PhyHT主要以包涵体形式存在于沉淀中;(2)通过优化表达条件,降低温度和诱导剂浓度均不能明显改善包涵体问题,通过构建分子伴侣共表达系统(即pG-KJE8、pGro7、pKJE7和pTf16 4种分子伴侣质粒分别与重组表达质粒pET28b-PhyHT共表达),筛选能提高目的蛋白可溶性表达的分子伴侣质粒;(3)包涵体经过复性和进一步的纯化,得到了高纯度的有生物活性的目的蛋白。

PhyH, a novel phytase from Bacillus sp. HJB17, successfully clone and express the truncated phytase PhyHT （ cancel the first 120 nucleotides which encode a 40 amino acid secreted signal peptide ） in Escherichia coli. To improve the soluble expression level of PhyHT, and get large-scale purified and active proteins, the expression conditions were optimized, including concentrations of IPTG and temperatures of induction. The co-expression system of pET28b-PhyHT and four molecular chaperone vectors（ pG-KJE8 ,pGro7, pKJE7, and pTfl6）were constructed respectively. Additionally, it was successful in vitro refolding of Bacillus phytase from the inclusion bodies. The results were described as follows： （1） the PhyHT gene was cloned into vector pET28b successfully ; the expressed proteins were found in the insoluble cytoplasmic fraction as inclusion bodies, even with different expression conditions. （2） Molecular chaperone vectors pGro7 and pKJE7 improved significantly the soluble protein level. （3） PhyHT with biological activity was obtained after the recombinant vector pET28b-PhyHT was expressed and renatured. Furthermore, the protein was purified through Ni-NTA and gel filtration chromatography. The soluble proteins provide a potential value for the further mechanistic study of the structure and function of PhyHT.