Abstract: To constructe the chimeric vector with the encoding gene of PAcA of S.mutans, catalytic region in glucosyltransferase and cholera toxin B subnnit, and to testify its expression in Escherichia coli. Methods: Obtaining target genes pacA, gtfB-cat and ctxB with specific primers and templates of plasmids pcDNA3-pac, pET-gtfB and pBS-ctxB;Construction of intermediate vectors T-pacA, T-cat and T-ctxB through T-A cloning;T-ctxB and pET32-a(+) were digested with double restriction enzymes EcoRI and XhoI to construct the recombinant vector pET-ctxB, T-pacA and pET-ctxB were digested with KpnI and BamHI to construct the recombinant vector pET-pacA- ctxB. Finally, T-cat and pET-pacA-ctxB were digested with BamHI and EcoRI to construct the recombinant vector pET-pacA-cat-ctxB. Results: pacA, gtfB-cat and ctxB are all inserted into the vector pET32-a(+) correctly through the tests of restriction enzyme digestion, PCR and sequencing respectively. Their ORFs didn’t be changed. The recombinant plasmid can express target protein in E.coli host strain BL21 (DE3) after induced by IPTG, and the molecular weight of the protein were consistent with the prediction. Conclusion: The recombinant plasmid pET-pacA-cat-ctxB was successfully constructed and it can be expressed in prokaryotic cells.

Key words: Streptococcus mutans, surface protein, glucosyltransferase, cholera toxin B subunit, prokaryotic expression