RESUMO
Objective To construct pET21a-sBAFF by cloning the extracellular regions of 134-285 amino acids of BAFF, a member of human TNF family, and then express the gene in prokaryotic cells and purify the expressed product.Methods cDNA of K562 cell line was used as the template to amplify sBAFF gene to construct pET21a-sBAFF.Expression of sBAFF in E.coli BL21 was induced by IPTG, and the expressed proteins were assayed by SDS-PAGE.The bacteria were analyzed by sonication, and the target proteins mainly existed as inclusion bodies.Then sBAFF was purified by Ni2 +-IDA affinity chromatography.SDS-PAGE electrophoreses displayed that the expressed sBAFF migrated with a relative molecular weight of 18000.ResuIts The induction parameters such as temperature and inducing time were optimized.The target protein accounted for 38.59%of the total bacterial proteins.After refolding, 38.14% of sBAFF proteins were polymerized as an active trimer.The dimer form of sBAFF, which is representative of wrongly refolded product, accounted for very few.ConcIusion The expression and purification of BAFF which formed active trimer after refolding pave the way for its further function study and provide a novel approach for the development of BAFF-targeted therapeutics for autoimmune diseases.