title: Effect of lacY expression on homogeneity of induction from the P(tac) and P(trc) promoters by natural and synthetic inducers.
abstract: The role of the Escherichia coli lactose permease (LacY) in the homogeneous induction of the lactose-inducible promoters P(tac) and P(trc) by the natural inducer lactose and the synthetic inducer isopropyl-beta-D-thiogalactopyranoside (IPTG) was investigated. Lactose requires active transport by LacY, whereas IPTG can freely penetrate the cell wall. In E. coli strains lacking a functional LacY, IPTG is required for induction of P(tac) and P(trc). In E. coli strains carrying a functional LacY, induction of P(trc) and P(tac) with intermediate concentrations of lactose gave rise to two subpopulations, one fully induced and one uninduced, whereas a single, fully induced population resulted when high inducer concentrations were used. In contrast, induction with IPTG gave rise to a single population of cells at all inducer concentrations in both lacY and lacY(+) strains.
authors.affiliation: Department of Chemical Engineering, University of California, Berkeley, California 94720-1462, USA.
authors.forename: Artem
authors.initials: A
authors.lastname: Khlebnikov
authors.forename: Jay D
authors.initials: JD
authors.lastname: Keasling
mesh_terms: D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D007544:Isopropyl Thiogalactoside; D026901:Membrane Transport Proteins / Q000235:genetics*; D009004:Monosaccharide Transport Proteins; D011401:Promoter Regions, Genetic; D027981:Symporters
chemical_list: D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D007544:Isopropyl Thiogalactoside; C021499:lactose permease