Iron chelator-inducible expression system for Escherichia coli

Abstract

The PentC promoter of the entCEBA operon encoding enzymes for enterobactin biosynthesis in Escherichia coli is tightly regulated by the availability of iron in the culture medium. In iron-rich conditions, the PentC promoter activity is strongly repressed by the global transcription regulator Fur (ferric uptake regulator), which complexes with ferrous ions and binds to the Fur box 19-bp inverted repeat. In this study, we have constructed the expression vector pOS2 containing the PentC promoter and characterized its repression, induction, and modulation by quantifying the expression of the lacZ reporter gene encoding β-galactosidase. β-Galactosidase activities of E. coli transformants harboring pOS2-lacZ were highly induced in the presence of divalent metal ion chelators such as 2,2′-dipyridyl and EDTA, and were strongly repressed in the presence of excess iron. It was also shown that the basal level β-galactosidase expression by the PentC promoter was drastically decreased by incorporating the fur gene into the expression vector. Since the newly developed iron chelator-inducible expression system is efficient and cost-effective, it has wide applications in recombinant protein production.