庚型肝炎病毒E2区cDNA在毕赤酵母中的表达及抗原性鉴定

从含有庚型肝炎病毒(GBVC/HGV)包膜蛋白E2 cDNA(559bp)的质粒pGEX\|E2中，扩增得到能够编码日本血吸虫谷胱甘肽硫转移酶(GST)和GBVC/HGV包膜蛋白E2的融合基因片段。将此长度为1324bp的DNA片段插入到酵母表达载体pPIC9K中，使之位于α因子信号肽下游，且与之同框。通过电激转化将构建的重组表达质粒pPIC9K\|GST\|E2插入到Pichia pastoris GS115菌株染色体中。筛选His\++Mut\+s表型的转化子，震荡培养，用05%甲醇诱导表达5d后，在培养液中得到表达的GSTE2融合蛋白。经过表达条件的优化，GSTE2蛋白可占培养液中总蛋白的50%。通过谷胱甘肽亲和层析柱纯化，GSTE2融合蛋白的纯度可达95%左右。以庚型肝炎病人血清为探针，进行免疫印迹及ELISA实验，结果表明该融合蛋白具有能被庚型肝炎病人血清特异性识别的抗原性。

Expression and Characterization of Envelope Protein 2 Gene of Hepatitis G Virus in Pichia pastoris

A cDNA fragment locating at the putative envelop protein 2(E2) region of GBV-C/HGV fused with Schistosoma japonicum, glutathione S-transferase(GST) was amplified with PCR from plasmid pGEX-E2. The amplified DNA fragment was inserted into plasmid pGEX-5X-1, at the downstream of the coding sequences of GST, in the same reading frame with the gene of GST. The fusion gene fragment of GST-E2 was amplified with PCR, using the recombinant plasmid pGEX-5X-1-E2 as the template. The amplified 1324 bp DNA fragment of GST-E2 was inserted into Pichia pastoris expression vector pPIC9K in reading frame with alpha-factor secreting signal peptide. The plasmid pPIC9K-GST-E2 was transformed into Pichia pastoris GS115 with electroporation. The transformants (His+ Muts) were selected and induced to express the 54kD GST-E2 fusion protein, which could be specially recognized by both the antisera directed against E2 and against GST. The GST-E2 fusion protein was purified with Sepharose 4B glutathione affinity chromatography to a purity of 95%. The expression was optimized to achieve the highest expression level of GST-E2 fusion protein which was accumulated up to 50% of total proteins in the culture supernatant. The GST-E2 protein derived from the recombinant Pichia pastoris was proved possessing antigenicity and high specificity by ELISA, probed with sera from the patients infected by GBV-C/HGV.