Non-physiological expression of UhpT does not lead to uncontrolled leakage of sugar phosphates out of Escherichia coli cells.
De-regulated expression of uhpT under control of the tac promoter, by increasing concentrations of isopropyl-thio-beta-D-galactoside, progressively inhibited the growth rate of Escherichia coli cells, to such an extent that growth was fully inhibited at 1 mM of the inducer. Significantly, additio of glucose 6-phosphate to the growth medium of the cells did not protect against this inhibition. Furthermore, efflux of sugar phosphates from the cells did not take place under these conditions, unless protonophoric uncouplers were added. We therefore conclude that the regulation of uhpT expression, i.e. via extracellular induction through a two-component system, did not evolve in order to prevent loss of essential metabolites from the cytoplasm under conditions when extracellular sugar phosphates are not available.
van de Zee
J R
JR
Department of Microbiology, E.C. Slater Institute, BioCentrum, Amsterdam, The Netherlands.
Postma
P W
PW
Hellingwerf
K J
KJ
D001692:Biological Transport / Q000502:physiology; D015153:Blotting, Western; D050260:Carbohydrate Metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002455:Cell Division / Q000502:physiology; D002701:Chloramphenicol / Q000494:pharmacology; D003470:Culture Media; D004734:Energy Metabolism / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D007544:Isopropyl Thiogalactoside; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D010710:Phosphates / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D013997:Time Factors
D003470:Culture Media; D005958:Glucosephosphates; D009004:Monosaccharide Transport Proteins; D010710:Phosphates; D011993:Recombinant Fusion Proteins; D007544:Isopropyl Thiogalactoside; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D019298:Glucose-6-Phosphate; D002701:Chloramphenicol