A novel phosphate-regulated expression vector in Escherichia coli

The ugp promoter ( p ugp ) responsible for expression of the binding-protein-dependent sn-glycerol-3-phosphate transport system in Escherichia coli was cloned into a small multicopy plasmid pTER5, a derivative of pBR322, between the transcription terminators rpoCt and t L1 . The resulting expression vector, pPH3, permits convenient insertion of structural genes containing their own translational-initiation regions, into the multiple-cloning site derived from the pUC19 plasmid. The efficiency and regulatory properties of p ugp were measured using xylE and lacZ as reporter genes, which code for the corresponding enzymes catechol-2,3-dioxygenase (C23O) and β-galactosidase (βGal), respectively. Enzyme activities were virtually completely repressed in the presencee of excess inorganic phosphates (P i) and high concentrations of glucose. Maximal induction was observed at limiting P i (