蓝藻抗病毒蛋白-N基因的克隆、表达、纯化及活性鉴定

Expression, purification and activity determination of cyanovirin-N

摘要:

蓝藻抗病毒蛋白-N (Cyanovirin-N，CVN) 具有强效抗HIV及其他包膜病毒活性，该蛋白序列特殊，难以重组制备，在大肠杆菌细胞质中形成包涵体。本研究根据大肠杆菌密码子偏好性对CVN原始核苷酸序列进行优化，通过多次PCR合成SUMO-CVN的全长DNA序列，构建pET3c-SUMO-CVN重组表达质粒，重组质粒转化大肠杆菌BL21(DE3)，获得表达菌株。通过对诱导剂浓度和诱导时间的优化，发现以0.5 mmol/L IPTG在20℃诱导24 h可获得最高表达，SDS-PAGE结果显示，SUMO-CVN为可溶性表达，表达量占菌体总蛋白的28％；经特异性的SUMO蛋白酶对融合蛋白进行酶切及两步Ni-NTA凝胶亲和层析可以得到纯度较高的重组CVN蛋白。ELISA结果表明，重组蛋白CVN与gp120蛋白有较高的亲和力。体外抗病毒活性实验表明，重组蛋白CVN在纳摩尔浓度具有很好的抗HSV-1和HIV-1/ⅢB活性；这为开发基于CVN的新型、高效抗病毒药物打下了基础。

Abstract:

Cyanovirin-N (CVN) is an 11 kDa anti-HIV protein originally isolated from extracts of a cyanobacterium, Nostoc ellipsosporum. The protein binds with high affinity to the viral envelope glycoprotein gp120 and irreversibly inactivates diverse HIV strains. A fusion gene consisting of cvn, sumo and 6xHis tag was synthesized by PCR according to the codon bias of Escherichia coli. The fusion protein is expressed in the cytoplasm of E. coli in a soluble form and up to 28% of the total protein. The recombinant CVN was purified to homogeneity by 2 rounds of Ni-NTA affinity chromatography and one round of SUMO protease cleavage. Bioactivity assay demonstrated that SUMO-CVN and CVN bound to gp120 with nanomolar concentration. In addition, CVN showed potent anti-HSV-1 and anti-HIV-1 activities in in vitro cellular assays. Therefore, the 6xHis SUMO fusion expression and purification system provides a better approach for large scale production of CVN for further microbicide development.