目的 在大肠杆菌中高效表达变异链球菌核糖-5-磷酸异构酶A( ribose 5-phosphate isomerase A,rpiA ),并对表达产物进行纯化和鉴定.方法 根据GenBank中变异链球菌UA159株基因组rpiA的DNA编码序列,设计PCR引物,扩增变异链球菌核糖-5-磷酸异构酶A的DNA编码序列,将其克隆至pGEX-6p-1载体中,构建重组质粒,将测序正确的重组质粒转化入大肠杆菌BL21 (DE3)中,用异丙基-β-D-硫代吡喃半乳糖苷(isopropyl β-D-1-thiogalactopyranoside,IPTG)诱导表达；对培养温度、IPTG用量、诱导时间等条件进行了优化；用亲和层析、离子交换层析纯化目标蛋白；用SDS-PAGE和质谱对目标蛋白进行鉴定.结果 变异链球菌核糖-5-磷酸异构酶A在大肠杆菌中高效、可溶性表达,经质谱鉴定及SDS-PAGE分析,表达产物为变异链球菌核糖-5-磷酸异构酶A蛋白.经过纯化,得到纯度高达95％的变异链球菌核糖-5-磷酸异构酶A.结论 成功地在大肠杆菌中高效表达了变异链球菌核糖-5-磷酸异构酶A蛋白,并建立了纯化工艺,得到高纯度的重组蛋白,为进一步研究变异链球菌属核糖-5-磷酸异构酶蛋白的生物学活性及功能奠定了基础.%Objective To express, purify and characterize the ribose 5-phosphate isomerase A(rpiA) from Streptococcus muians. Methods A DNA fragment encoding S. mutans ribose 5-phosphate isomerase A was amplified by PCR using the genomic DNA of Streptococcus mutans UA159 as a template. The PCR product was cloned into vector pGEX-6p-l. The construct carrying the coding DNA sequence of rpiA fused with GST was transformed into E. coli BL21 (DE3) , and the fusion protein was expressed by induction with IPTG. The recombinant protein was purified by affinity chromatography and ion exchange chromatography. The purified target protein was identified by SDS-PAGE and MALDI-TOF MS. Results S. mutans ribose 5-phosphate isomerase A was successfully expressed in E. coli in soluble form. After a series of purifications, we got the recombinant protein with the purity higher than 95%. The product was identified to be S. muians ribose 5-phosphate isomerase A by SDS-PAGE and MALDI-TOF-TOF MS. Conclusion 5. muians ribose 5-phosphate isomerase A was successfully expressed in E. coli. An effective purification protocol was established. Recombinant rpiA with a purity higher than 95% was obtained, which provided a basis for the further studies of the biological activities and functions of ribose 5-phosphate isomerase A.
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