Rv2742 is a novel gene identified from Mycobacterium tuberculosis H37Rv by the proteogenomics strategy. The aim of this study was to establish a system of soluble expression and purification of the missing protein Rv2742 in M. tuberculosis H37Rv, to provide reference for further research on the biological function of Rv2742. The soluble protein was not successfully induced by prokaryotic expression vectors pGEX-4T-2-Rv2742, pET-32a-Rv2742, pET-28a-Rv2742 and pMAL-c2X-Rv2742. After the codon of novel gene Rv2742 was optimized according to E. coli codon usage frequency, only the recombinant strain containing plasmid pMAL-c2X-Rv2742 could produce soluble products of Rv2742 encoding gene. In addition, the expression effects of the desired fusion protein were also analyzed under different conditions including hosts, culture temperatures and IPTG concentrations. The optimum expression conditions were as follows: Rosetta (DE3) host, 16 °C culture temperature and 0.5 mmol/L IPTG. After being purified by affinity chromatography with amylose resin, the fusion protein sequence was confirmed by LC-MS/MS. These results indicated that the novel gene Rv2742 product could be successfully induced and expressed in a soluble form by the expression system pMAL-c2X with MBP tag. Our findings provide reference for studies on potential interaction and immunogenicity.
Rv2742 是本课题组前期基于蛋白质基因组学策略从结核分枝杆菌Mycobacterium tuberculosis H37Rv 中发现、鉴定的遗漏注释基因。文中旨在建立结核分枝杆菌H37Rv 漏注释蛋白Rv2742 的可溶性诱导表达、纯化体系，为进一步探索Rv2742 基因参与的生物学功能奠定基础。前期实验发现构建的pGEX-4T-2-Rv2742、pET-28a-Rv2742、pET-32a-Rv2742 及pMAL-c2X-Rv2742 原核表达载体均无法实现目的蛋白的诱导表达。但经密码子优化后，仅有pMAL-c2X-Rv2742 载体能够实现目的蛋白的可溶性诱导表达。此外，通过比较不同宿主菌、温度及IPTG 浓度对目的蛋白表达量的影响，发现目的蛋白在Rosetta (DE3)中，16 ℃及 0.5 mmol/L IPTG 诱导条件下表达量最高。直链淀粉树脂 (Amylose resin) 亲和层析柱纯化获得较纯的产物，经LC-MS/MS 验证确认是Rv2742 融合蛋白肽段序列。成功获得结核分枝杆菌H37Rv 新基因Rv2742的重组蛋白，可进一步开展其潜在相互作用及免疫原性研究工作。.
Keywords: Mycobacterium tuberculosis; affinity purification; novel gene; prokaryotic expression.