Prokaryotic expression and purification of human Smith D1 antigen / 中华检验医学杂志

Objective To obtain recombinant human Smith D1 (Sm D1) antigen and establish detecting assay.Methods Human Smith D1 antigen was synthesized by PCR using human Leukemic cDNA. The prokaryotic expression vector pGEX-ST-Sm D1 was constructed and transformed into E.coli.BL21 cell.Protein expressed under the induction of IPTG.We established DIGFA for detecting anti-Sm D1 antibodies with purified Sm D1 antigens.Results Sequence and restriction analysis revealed Sm D1 gene was cloned in frame into pGEX-5T,SDS-PAGE profile showed a clear protein band with a relative molecular weight of 39 000 and western blotting indicated that the expressed product specifically reacted to polyclonal anti-human Sm D1 genes.There was no significant difference between DIGFA and IB.The agreement between DIGFA and IB was 91.7% as calculated by Kappa statistical method.The sensitivity and specificity of DIGFA were 100% and 83.3% repectively.Conclusions Human Sm D1 gene is successfully cloned、 expressed and purification.The DIGFA,using purified Sm D1 antigens,is as good as IB,rather simpler, more rapid and reliable assay.

Eukaryotic Expression and Primarily Application of Human Smith D1 Antigen in Methylotrophic Yeast Pichia pastoris / 微生物学通报

To clone, express and primarily use human autoantigen Sm D1 in methylotrophic yeast Pichia Pastoris. The gene Sm D1 was cloned by PCR.The PCR product was inserted into the vector pPIC9k. The recombinant plasmid pPIC9k- Sm D1 was transformed into yeast SMD1168 by electroporation. The positive clones were screened in MD plates. The high copy number transformants were rapidly selected by using G418 and were induced by methanol. Supernatants after induction were analyzed by SDS-PAGE and im-munodot. The PCR product was showed about 360 bp in size which was in accordance with predicted. The pPIC9k-Sm D1 showed the same seqencing result with GenBank’s report and restriction enzyme analysis confirmed our prediction. The pPIC9k-Sm D1 positive clone produced an about 16 kD protein which had natural immunogenicity of human autoantigen Sm D1 by SDS-PAGE and immunodot. The sensitivity and specificity of immunodot were 96% and 100%, respectively. The agreement between immunodot and im-munoblot was 98%. Successfully cloning and high-level expression of human autoantigen Sm D1 in methy-lotrophic yeast Pichia pastoris laid a foundation for further research work.