[Expression, purification and characterization of HbsAg binding protein in Pichia pastoris]

Human hepatitis B virus surface antigen (HBsAg) binding protein(SBP) shows a specific binding ability to HBV surface antigen HBsAg. Previous work proved an ability of SBP to enhance the immune response of HBsAg vaccine. To investigate the function and mechanism of this protein, we constructed SBP-expression strains with Pichia pastoris expression system. We screened these strains and have got an expression strain with high protein expression quantity. Fermentation product was collected and purified to gain a large amount of purified protein. Identification of purified SBP with SDS-PAGE, High performance liquid chromatography, Western blotting and mass spectrometry suggested that the protein was highly purified and with a good integrity. ELISA test of purified SBP showed a significant binding ability to HBsAg, suggesting a good protein activity. This work offers a solid foundation to the research of SBP function and mechanism of immune enhancement.