沙眼衣原体多形外膜蛋白PmpI的原核表达、纯化、抗体制备及鉴定

Polymorphic membrane protein I of Chlamydia trachomatis：prokaryotic expression, purification, antibody preparation and identification

目的：克隆、表达沙眼衣原体多形外膜蛋白I（PmpI）基因，并进行免疫原性鉴定，分析其生物学特征。方法用生物信息软件分析沙眼衣原体多形外膜蛋白PmpI的基因序列并预测PmpI蛋白的B细胞抗原表位。以D型沙眼衣原体DNA为模板，PCR扩增PmpI基因N端90~1464碱基序列，构建原核载体进行诱导表达。Ni离子亲合层析柱纯化重组蛋白，制备PmpI多克隆抗体并用Western印迹法检测其免疫原性。结果对蛋白质的二级结构和柔性区、氨基酸的亲水性、抗原指数和表面可及性预测结果综合分析，推测该蛋白含有8个优势B细胞表位。PCR扩增D型沙眼衣原体PmpI基因核苷酸序列长度为1375 bp。成功构建pET28a-PmpI原核表达重组体，经诱导表达、亲和层析纯化后获得了相对分子质量为50000的重组蛋白并制备其多克隆抗体。结论成功克隆并表达了D型沙眼衣原体多形外膜蛋白N-PmpI，为研究该蛋白的生物学功能奠定了一定基础。

Objective To clone and express the polymorphic membrane protein I（PmpI）gene of Chlamydia trachomatis（Ct）, and to assess the immunogenicity and biological characteristics of PmpI. Methods A bioinformatic software was used to analyze the sequence of the PmpI gene of Ct, and to predict B cell epitopes in PmpI. With Ct serovar D DNA as the template, PCR was performed to amplify the N-terminal region（from position 90 to 1464）of the PmpI gene, which was cloned into a prokaryotic expression vector pET28a to express the recombinant protein PmpI. A Ni-ion affinity chromatography column was used to purify the recombinant protein, which was used to immunize New Zealand rabbits for preparation of polyclonal antibodies. Western blot analysis was conducted to evaluate the immunogenicity of this protein. Results A comprehensive analysis was carried out on the secondary structure, flexible regions, hydrophilicity plot, antigenic index and surface probability plot of the protein, which suggested that PmpI had 8 dominant B-cell epitopes. The product of PCR targeting the PmpI gene of Ct serovar D showed a total length of 1 375 bp. The recombinant prokaryotic expression vector pET28a-PmpI was successfully constructed. A recombi-nant protein with a relative molecular mass of approximately 50 000 was successfully expressed after isopropylβ-d-1-thiogalactopyranoside （IPTG） induction, and purified by affinity chromatography. Polyclonal antibodies against the recombinant protein were successfully prepared. Conclusion The N-PmpI protein of Ct serovar D is cloned and expressed successfully, laying a foundation for further studies on its biological functions.