A dual prokaryotic (E. coli) expression system (pdMAX)

In this study, we introduced an efficient subcloning and expression system with two inducible prokaryotic expression promoters, arabinose and lac, in a single plasmid in Escherichia coli. The arabinose promoter unit allows for the expression of a FLAG-tagged protein, while the isopropyl-β-D-thiogalactoside (IPTG)-inducible unit allows for the expression of a Myc-tagged protein. An efficient subcloning (DNA insertion) system (iUnit) follows each promoter. The iUnit, based on a toxin that targets DNA topoisomerase of E. coli, allows for effective selection with arabinose or IPTG induction. With the dual promoter plasmid (pdMAX) system, expressed lacZ (β-galactosidase) activity was significantly decreased compared with the original solo expression system. Despite this disadvantage, we believe that the pdMAX system remains useful. A recombinant plasmid (pdMAX/ara/DsRed/IPTG/EGFP; pdMAX/DsRed/EGFP) with DsRed in the arabinose expression unit and EGFP in the IPTG expression unit showed fluorescent protein expression following additional low-temperature incubation. Thus, the novel pdMAX system allowed efficient subcloning of two different genes and can be used to induce and analyze the expression of two distinct genes. The proposed system can be applied to various types of prokaryotic gene expression analysis.