Aims To construct the N-terminal Strep-tagged ( NS-tagged) fusion protein expression vector, and to apply the vector to express NS-tagged fusion proteins of Chlamydia RNA polymerase subunit. Meth-ods By using PCR method, NS fusion protein tag and a new multiple cloning sites (MCS) were inserted into pET21c-DH plasmid by primers to replace the original T7 protein tag and MCS. The newly introduced Not I cutting site was chosen for self-ligation of PCR prod-uct. Then, the cyclized PCR product was transformed into DH-5α competent cells. The positive clones were selected by PCR and sequencing. To get NS-tagged fu-sion proteins of chlamydial RNA polymerase subunits, the α, β and β′ subunits were inserted between BamH I and Sal I cutting sites of the newly constructed ex-pression vector. Then, the NS-α, NS-β and NS-β′ ex-pression vectors were transformed into Arctic Express expression cells. The fusion protein expression statuses of transformed cells were identified by Commassie blue staining and Western blot. Results The NS-tagged fusion protein expression vector pET21c-NS-MCS was successfully constructed, and NS-α, NS-β and NS-β′fusion proteins were obtained by using this newly con-structed expression vector. Conclusions In this pro-ject, we constructed an NS-tagged fusion protein ex-pression vector and applied it to express NS-α, NS-βand NS-β′ fusion proteins. Our study can lay a solid foundation for the study of transcriptional regulation of Chlamydia genes.%目的：构建携带 N 末端 Strep(NS)蛋白标签的表达载体；在表达载体中构建衣原体 RNA 聚合酶亚基重组蛋白并表达。方法采用 PCR 的方法,通过引物引入 NS 蛋白标签和新的多克隆位点替代 pET21c-DH 质粒中原有的 T7蛋白标签和多克隆位点,选择新引入的 Not I 酶切位点进行 PCR产物的环化自连,转化 DH-5α细菌后筛选阳性菌株,PCR 法和基因测序法鉴定新构建的表达载体；在新构建表达载体的BamH I 和 Sal I 位点之间分别插入衣原体 RNA 聚合酶核心酶的α、β、β′亚基,获得表达 NS-α、NS-β、NS-β′融合蛋白的表达载体,转化表达菌株 ArcticExpress,筛选阳性表达菌株,并用考马斯亮蓝染色、Western blot 等法鉴定融合蛋白的表达情况。结果成功构建了携带 NS 蛋白标签的 pET21c-NS-MCS 载体,并成功将其应用于衣原体 RNA 聚合酶核心酶亚基融合蛋白的构建及表达。结论获得稳定表达 NS-α、NS-β、NS-β′融合蛋白的表达载体,为研究衣原体基因转录调控奠定了良好的基础。
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