Human β2-microglobulin expression and purification in Escherichia coli

Human β2-microglobulin(β2m) is a light chain of major histocompatibility complex(MHC) class-Ⅰ molecule.Expression and purification of this protein in Escherichia coli(E.coli) is a prerequisite to the preparation of MHC-Ⅰ molecule.The expression vector pET23a+β2m was presented,in which the complete sequence of β2m gene was inserted.Constant-yield expression of β2m was achieved in E.coli transformed with the expression vector,and most of the recombinant β2m existed in the inclusion body after IPTG induction.The inclusion body was washed extensively and β2m in the inclusion body was solublized with 6 M urea.The β2m was refolded by dialysis and purified by ion-exchange chromatography(Q-Sepharose).Western blotting assay indicated that the polyclonal antibody against human native β2m could react specifically with the recombinant protein.The purified protein appeared as a single band on both SDS-PAGE and Western blotting,indicating that it was chemical and antigenic pure.This work provides the basis for the further study of MHC-Ⅰ molecule.