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将外源基因———日本血吸虫２６ｋＤ抗原（Ｓｊ２６ＧＳＴ）基因克隆到大肠杆菌分枝杆菌穿梭质粒中，构建成四个不同的表达截体，研究它们在耻垢后分枝杆菌（Ｍｙｃｏｂａｃｔｅｒｉｕｍｓｍｅｇｍａｔｉｓ）中的表达效率。首先将含有结核杆菌热休克蛋白７０（ＨｅａｔＳｈｏｃｋＰｒｏｔｅｉｎ，ＨＳＰ７０）的启动子的质粒ｐＭＴ７０用ＮｃｏＩ切，进行两种不同的修饰后，得到不同的ＳＤ序列；将Ｓｊ２６ＧＳＴ基因克隆进去。再将含ＨＳＰ７０启动子和Ｓｊ２６ＧＳＴ基因的片段切下，克隆到分枝杆菌大肠杆菌穿梭质粒ｐＢＣＧ２０００中，筛选出不同ＳＤ序列、不同方向和不同拷贝数的分枝杆菌表达载体四个。所表达的重组天然Ｓｊ２６ＧＳＴ（ｒＳｊ２６ＧＳＴ）为可溶性蛋白，在ＳＤＳＰＡＧＥ上分子量为２６ｋＤ处可见明显的表达蛋白带。通过薄层扫描分析，发现表达质粒中双拷贝启动子外源基因组合，表达效率最高，是单拷贝组合的１６倍，占分枝杆菌菌体总蛋白的２８％。而不同的克隆方向和不同的ＳＤ序列（两者相差３个碱基）对表达效率的影响不明显。
The exogenous gene - Schistosoma japonicum 26kD antigen (Sj26GST) gene was cloned into shuttle plasmid E. coli Mycobacterium, and was constructed into four different expression intercepts, to study their Mycobacterium smegmatis ) In the expression efficiency. First, the plasmid pMT70 containing the promoter of Mycobacterium tuberculosis heat shock protein 70 (HSP70) was cut with NcoI and subjected to two different modifications to obtain different SD sequences; the Sj26GST gene was cloned into it. Then fragments containing HSP70 promoter and Sj26GST gene were excised and cloned into mycobacterium shuttle E.coli plasmid pBCG2000 to screen out four mycobacterial expression vectors with different SD sequences, different orientations and different copy numbers. The expressed recombinant natural Sj26GST (rSj26GST) is a soluble protein, and a clear expression protein band can be seen at a molecular weight of 26 kD on SDS-PAGE. Through the thin-layer scanning analysis, it was found that the double copy promoter-exogenous gene combination in the expression plasmid had the highest expression efficiency, which was 1.6 times of the single copy combination and accounted for 28% of the total protein of mycobacteria. However, the effect of different cloning directions and different SD sequences (3 bases difference between them) on the expression efficiency was not obvious.