乙型肝炎病毒核心抗原的原核表达及纯化

Prokaryotic Expression and Purification of Hepatitis B Virus Core Antigen

目的原核表达乙型肝炎病毒核心抗原(HBcAg),纯化HBcAg病毒样颗粒(Virus-like particle,VLP),并对其理化性质进行鉴定。方法根据大肠杆菌密码子偏爱性对HBcAg基因进行密码子优化,全基因合成优化基因,克隆至载体pET-32a(+)中,构建原核表达质粒pET-HBcAg,转化大肠杆菌BL21(DE3),IPTG诱导表达。重组蛋白经盐析和层析纯化后,经SDS-PAGE、Western blot、电镜观察、等电点分析、高效液相色谱(HPLC)分析和N-末端氨基酸测序等进行鉴定。结果重组表达质粒经酶切和测序鉴定证明构建正确;表达的重组蛋白相对分子质量约为21 000,为可溶性表达,表达量占菌体总蛋白的21.6%;纯化后其纯度可达99.4%,具有良好的反应原性,VLP形成良好,结构均一,等电点在pH 6.0～6.9之间,HPLC分析形成T3和T4两种不同结构,N-末端序列正确,无氨基酸降解。结论已成功构建了HBcAg原核表达质粒,并获得了高纯度的HBcAgVLP,为进一步研究HBcAg VLP的生物学特性奠定了基础。

Objective To express hepatitis B virus core antigen（HBcAg） in prokaryotic cells,purify the virus-like particles（VLPs） and analyze their physic-chemical property.Methods The codon of HBcAg was optimized according to the E.coli-perference,then synthesized and cloned into vector pET-32a（＋）.The constructed prokaryotic expression vector pET-HBcAg was transformed to E.coli BL21（DE3） for expression under induction of IPTG.The expressed recombinant protein was purified by salting out and chromatography,and identified by SDS-PAGE,Western blot,electron microscopy,isoelectric point analysis,HPLC and N-terminal amino acid sequencing.Results Restriction analysis and sequencing proved that recombinant expression vector was constructed correctly.The expressed recombinant protein in a soluble form,with a relative molecular mass of about 21 000,contained 21.6% of total somatic protein.The purified recombinant protein reached a purity of 99.4% and showed good antigenicity.VLPs with uniform structure were formed,of which the isoelectric point ranged from pH 6.0 to pH 6.9.HPLC showed T3 and T4 structures and correct sequence at N-terminus of HBcAg but no amino acid degradation.Conclusion The prokaryotic expression vector for HBcAg was successfully constructed,and highly purified HBcAg VLPs were obtained,which laid a foundation of further study on biological characters of HBcAg VLPs.