Abstract
BackgroundCell 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.ResultsWe 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.ConclusionsThis 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.
Highlights
Cell surface display systems enable recombinant proteins to be displayed on the surface of microorganisms to bind external substrates and protect cells from membrane penetration of substrates
Bioprocess. (2019) 6:14 family of bacterial proteins composed of an N-terminal passenger domain and a C-terminal β-barrel-forming domain that is integrated into the outer membrane and facilitates the surface display of the passenger domain (Jose 2006)
AT systems are considered to have some striking advantages compared to other surface display systems: a higher number of recombinant proteins can be displayed at the cell surface without reducing cell viability; the β-barrel is freely mobile while serving as an anchor for the recombinant protein within the outer membrane; and an inorganic prosthetic group can be incorporated in an expressed apo-protein (Jose 2006)
Summary
We introduced two fusion sites which are unstructured domain (52–138 aa) and autochaperone domain (600–700 aa) at N-terminal for passenger proteins. 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 endo‐ glucanase, whole-cell surface-displayed Ag43-138-BsCel showed the highest specific activity which was 4.65-fold of BsCel. Cell-displayed cellulase preserved residual activity ranging from 78% to 38% at temperatures from 55 °C to 80 °C, respectively
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