ABSTRACT
Objective:To construct a surface display system containing various lengths of the Ag43 passenger domain for an optimal bacterial surface display of foreign protein HPV16L1.Methods:(1) Ag43 gene sequences of different lengths were inserted into pET22b vector to construct four Ag43 surface display vectors (Ag43/138, Ag43/551, Ag43/552 and Ag43/700) using PCR and subcloning strategy. (2) The generation of four HPV16L1-Ag43 fusion constructs was completed by PCR and subcloning methods. (3) HPV16L1-Ag43 fusion proteins were expressed and analyzed by SDS-PAGE. (4) The surface exposure of HPV-16L1 was verified using trypsin digestion.Results:PCR analysis and sequencing results showed that Ag43 surface display vectors and HPV16L1-Ag43 fusions were constructed successfully. SDS-PAGE showed that the expression of HPV16L1-Ag43 fusion proteins could be induced with 0.2 mmol/L IPTG and the protein content was reduced after the cells were treated with trypsin, especially the content of Ag43/700-HPV16L1 that showed a drastic reduction.Conclusions:The Ag43 surface display system was successfully constructed and could be used for a successful display of HPV16L1. This study also showed that Ag43/700 comprising only the α-helix and the β-barrel of Ag43 provided an optimal surface display for HPV16L1.
ABSTRACT
Objective To construct a recombinant Escherichia coli ( E. coli) with surface-dis-played lead specific binding protein PbrR and to further study intestinal colonization by the recombinant bac-teria in mice and gastrointestinal tolerance of the bacterial surface-displayed PbrR. Methods Chimeric pro-tein Lpp-OmpA coding sequence was chemically synthesized and inserted into the expression vector pET-21a to construct the outer membrane display vector pLOA. PbrR coding sequence was also obtained by chemical-ly synthesis and inserted into pLOA to generate the outer membrane display plasmid pLOA-pbrr. E. coli BL21 (DE3)pLysS was transformed with pLOA-pbrr and induced by IPTG. The expressed recombinant proteins were analyzed by 15% SDS-PAGE and Western blot assay. Lead adsorption capacity of the cell surface-dis-played PbrR in the simulated intestinal juice and tolerance of the recombinant E. coli to simulated gastric juice were analyzed, respectively. KM mice were orally given the induced recombinant bacteria by gastric lavage for 7 consecutive days and then were continually fed until day 30. The contents of recombinant bacte-ria in stool samples were detected by dilution plate method on day 7, 15 and 30. The recombinant protein with His tag was detected by immunoblotting on day 7 and 15. Results Based on Lpp-OmpA, the PbrR outer membrane display vector was successfully constructed. The recombinant fusion protein Lpp-OmpA-PbrR-His tag was highly expressed in E. coli. The recombinant E. coli strains displaying PbrR on their outer membrane accumulated a significant level of Pb2+ in simulated intestinal juice. Moreover, those strains showed a tolerance to gastric acid in vitro and could colonize in the intestinal tracts of mice via oral infection. The surface-displayed recombinant fusion protein showed a better tolerance to the environment of digestive tract. Conclusion The recombinant E. coli strain displaying PbrR on its surface showed a stronger capabili-ty of lead accumulation from simulated intestinal environment and could colonize in the intestinal tracts of mice. The surface-displayed recombinant PbrR also showed a good tolerance to digestive juice. This study paved the way for further researches on the selective elimination of lead by biosorption based on animal mod-els.