金黄色葡萄球菌蛋白A(SpA)Z结构域串联体的克隆、表达和筛选

Cloning,expression and screening tandem repeats of the Z domain of Staphylococcus aureus protein A

筛选一种高效重组金黄色葡萄球菌蛋白A(SpA)用于制备抗体纯化亲和介质。首先通过基因操作获得金黄色葡萄球菌蛋白A(SpA)的Z结构域单体、二串体、三串体、四串体和五串体基因,将目的基因分别克隆至pET-22b表达载体并转化至大肠杆菌BL21(DE3)感受态细胞,获得不同串联个数的Z结构域基因工程菌,经诱导表达和Ni2+亲和层析纯化得到Z结构域单体和二-五串体蛋白。纯化后的目的蛋白偶联至琼脂糖凝胶作为亲和层析介质,对人免疫球蛋白G(IgG)进行分离纯化。分析比较Z结构域串联体蛋白产量及其偶联的亲和介质对抗体吸附载量的差异。结果表明,构建的Z结构域单体、二串体、三串体、四串体和五串体基因工程菌能有效表达目的蛋白,制备的凝胶亲和介质可特异性吸附人IgG。增加Z结构域串联数,重组蛋白产量和单位摩尔数多聚体蛋白吸附载量获得提高,其中,重组四串体蛋白产量大(160 mg/10 g湿菌体),对抗体的吸附载量高(34.4 mg人IgG/mL胶),更适合作为配基用于亲和层析介质的制备。

To screen an efficient recombinant Staphylococcus aureus protein A （SPA） for preparing matrix for affinity purification of immunoglobulin G （IgG）, a genetic engineering approach was used to obtain monomer, two, three, four and five tandem repeats genes of the Z domain of SpA, then the genes were cloned into expression vector pET-22b and subsequently expressed in Escherichia coli BL21 （DE3）. After induction with lactose, the target proteins were purified by Ni2＋ affinity chromatography. The proteins with two, three, four and five tandem repeats of the Z domain were then coupled to CNBr-activated Sepharose 4B as an affinity chromatography matrix for affinity purification of human IgG. Furthermore, the differences in protein yield and IgG-binding capacity at different recombinant proteins were analyzed. The target proteins with monomer and tandem repeats of the Z domain had an effective expression in the genetic engineering bacteria. IgG could be specifically absorbed from human plasma by affinity chromatography. The protein yield and amount of IgG absorption of per mole protein could be improved by increasing the tandem repeats number of the Z domain. Compared with other tandem repeats, four tandem repeats of the Z domain exhibited more protein yield （160 mg/10 g wet cells） and higher level of IgG absorption （34.4 mg human IgG/mL gel）. Therefore, four tandem repeats of the Z domain is more suitable for preparing matrix for affinity purification of IgG.