猪链球菌2型人源分离株截短的溶菌酶释放蛋白基因的克隆及原核表达

目的:克隆及表达猪链球菌2型(S.suis2)人源分离株Habb截短溶菌酶释放蛋白(MRP)基因。方法:根据S.suis2mrp基因的序列设计引物,克隆和分析江苏海安患者分离株Habb截短mrp基因(tmrp),构建原核表达质粒pGEX4T-2-mrp。在大肠杆菌中诱导带有谷胱甘肽转移酶(GST)标签的融合蛋白tMRP-GST表达;经亲和层析法纯化后,用凝血酶酶切去除重组蛋白中的GST,制备纯化的截短MRP(tMRP)抗原。用Westernblot检测重组抗原的活性。结果:序列分析表明,获得的tmrp基因长957bp;原核表达的融合蛋白tMRP-GST的相对分子质量(Mr)约61000;凝血酶处理的tMRP抗原的Mr约为35000。Westernblot分析显示,MRP-GST、tMRP蛋白均可与MRP多克隆抗血清发生特异性反应。结论:成功地克隆人源分离株Habb截短的mrp基因,并在原核系统实现高效表达,制备的纯化抗原tMRP具有良好的抗原性,为开展相关免疫学研究奠定了基础。

Cloning and prokaryotic expression of truncated muramidase-released protein gene of human Streptococcus suis type 2

AIM: To clone and express the truncated Habb mrp gene of human Streptococcus suis type 2 (S.suis 2) and detect its activity. METHODS: A pair of primers based on S.suis 2 mrp gene were schemed out. The turncated mrp (tmrp)gene of S.suis 2 strain Habb isolated from diseased person in Haian, Jiangsu province was cloned and analyzed. The prokaryotic expression plasmid pGEX4T-2-tmrp was constructed.The expression of recombinant protein with glutathione S-transferase (GST) was induced in E.coli TG1. The fusion protein (tMRP-GST) was purified by affinity chromatography, and the GST was cut from tMRP-GST with thrombin protease to gain the truncated MRP (tMRP) antigen. The activity of recombinant protein was analyzed by Western blot. RESULTS: Sequence analysis showed that the length of the truncated mrp was 957 bp. The prokaryotic expressed production was a fusion protein, whose molecular weight was about 61 kD, and the molecular weight of the purified tMRP protein was about 35 kD. Western blot analysis showed that tMRP-GST and tMRP were detected specifically by MRP antiserum on nitrocellulose membrane. CONCLUSION: The truncated mrp gene of human S.suis 2 strain Habb is successfully cloned, and the high expression of the functional recombinant protein is achieved in the prokaryotic system, which facilitates the further studies on the bio-function and immunology.