Antigen-43-mediated surface display revealed in Escherichia coli by different fusion sites and proteins

Background Cell surface display system allows for endowing functional proteins expressed on bacterial surface by fusing different anchor proteins. Among PgsA, Blc, and Omp anchor, the antigen 43 (Ag43)-mediated surface display is a novel system in Escherichia coli . Here, we have demonstrated the red fluorescent protein (RFP) and cellulase (EC 3.2.1.4) on the cell surfaces at two different fusion sites in Ag43. Results We introduced two fusion sites which are unstructured domain (52–138 aa) and autochaperone domain (600–700 aa) at N-terminal for passenger proteins. As a result, the surface-displayed RFP expressed in plasmid pET28a, but the intracellular RFP expressed more than the surface-displayed RFP. Improved display efficiency of Ag43 was present when fusing at the site of the 138th amino acid (aa) compared to fusing at the site of the 700th aa. For endoglucanase, whole-cell surface-displayed Ag43-138-BsCel5 showed the highest specific activity which was 4.65-fold of BsCel5. Cell-displayed cellulase preserved residual activity ranging from 78% to 38% at temperatures from 55 °C to 80 °C, respectively. Conclusions This study is to demonstrate the novel surface display system of Ag43 in E. coli by targeting two different proteins RFP and BsCel5 that were successfully displayed on the cell surfaces at two different fusion sites. The Ag43 system displays surface heterologous proteins and is a potential whole-cell catalyst in the bioconversion of cellulose.