猪链球菌IgG结合蛋白的原核表达及其与不同动物IgG的结合性

Prokaryotic expression of recombinant Streptococcus suis IgG binding protein and its binding activity with IgG

猪链球菌IgG结合蛋白(SPG)是一种可与多种动物IgG结合的细胞壁蛋白,广泛地存在于猪链球菌的各个血清型中,被认为是共同抗原。然而其在猪链球菌中的生物学意义并不清楚。本实验用PCR方法从猪链球菌1/2、1、2和9型菌株基因组中扩增SPG基因,构建pET28a-SPG重组表达载体,将其转入大肠杆菌BL21菌株。IPTG诱导表达后,重组蛋白经SDS-PAGE及Western blotting鉴定为可高效表达。镍亲和层析及分子筛两步纯化后获得纯度较高的目的蛋白。Western blotting及ELISA试验结果表明,所有纯化的目的蛋白均可与不同动物IgG结合,其中与人和猪IgG的结合能力相对较高,但不同血清型猪链球菌SPG与同种动物IgG的结合活性没有明显差异。

Streptococcus suis （S. suis） IgG-binding protein （SPG） was present in all S. suis strains examined. It showed binding activities with IgG from various host species. Little was known about the biological role of this protein, but it was commonly believed that it acted as virulence factor. In this study, the genes encoding SPG were amplified respectively from the total DNA of the S. suis serotype 1/2, 1, 2 and 9 with PCR and expressed in Escherichia coli BL21 by plasmid pET28a as vector. The recombinant proteins were first purified with affinity chromatography （Ni-NTA）, and further purified by sephadexG-200 gel chromatography. The recombinant SPG proteins were identified to have binding activities with IgG of different host species, and for human and porcine IgG they showed better binding activities. But the SPG from different serotypes of S. suis showed no great differences in their binding activities with IgG from the same host species.