Current Microbiology

, Volume 36, Issue 6, pp 341–347

The Effect of the lacY Gene on the Induction of IPTG Inducible Promoters, Studied in Escherichia coli and Pseudomonas fluorescens

  • Lars H.  Hansen
  • Steen  Knudsen
  • Søren J.  Sørensen

DOI: 10.1007/s002849900320

Cite this article as:
Hansen, L., Knudsen, S. & Sørensen, S. Curr Microbiol (1998) 36: 341. doi:10.1007/s002849900320

Abstract.

The role of the Escherichia coli lacY gene product (the lactose permease) in the induction of isopropyl-β-D-thiogalactopyranoside (IPTG) inducible promoters was studied in E. coli and P. fluorescens. This was done by comparing strains containing a lacIPOZYA chromosomal insert with newly constructed strains containing inserts without the lacY gene (lacIPOZ). The lactose operon inserts were introduced as single-copy chromosomal inserts to eliminate differences in expression caused by differences in copy number. Comparison between the two types of inserts showed that the lactose permease was essential to allow growth on lactose by both bacteria and that the lactose permease plays an important role in transporting the inducer IPTG across the membrane of P. fluorescens. The use of a functional lactose permease allows expression of β-galactosidase to increase more than fivefold from a wild-type lac promoter in P. fluorescens SS1001. We suggest that an increase in the rate of protein synthesis from lac-type promoters could be enhanced if an active lactose permease is present as well.

Copyright information

© Springer-Verlag New York Inc. 1998

Authors and Affiliations

  • Lars H.  Hansen
    • 1
  • Steen  Knudsen
    • 1
  • Søren J.  Sørensen
    • 1
  1. 1.Department of General Microbiology, Institute of Molecular Biology, University of Copenhagen, Sølvgade 83 H, DK1307 Copenhagen K, Denmark DK