title: Physiological consequences of DnaK and DnaJ overproduction in Escherichia coli.
abstract: The physiological consequences of molecular chaperone overproduction in Escherichia coli are presented. Constitutive overproduction of DnaK from a multicopy plasmid containing large chromosomal fragments spanning the dnaK region resulted in plasmid instability. Co-overproduction of DnaJ with DnaK stabilized plasmid levels. To examine the effects of altered levels of DnaK and DnaJ in a more specific manner, an inducible expression system for dnaK and dnaJ was constructed and characterized. Differential rates of DnaK synthesis were determined by quantitative Western blot (immunoblot) analysis. Moderate levels of DnaK overproduction resulted in a defect in cell septation and formation of cell filaments, but co-overproduction of DnaJ overcame this effect. Further increases in the level of DnaK terminated culture growth despite increased levels of DnaJ. DnaK overproduction was found to be bacteriocidal, and this effect was also partially suppressed by DnaJ. The bacteriocidal effect was apparent only with cultures which were allowed to enter stationary phase, indicating that DnaK toxicity is growth phase dependent.
authors.affiliation: School of Biological Sciences, University of Nebraska, Lincoln 68588-0018.
authors.forename: P
authors.initials: P
authors.lastname: Blum
authors.forename: J
authors.initials: J
authors.lastname: Ory
authors.forename: J
authors.initials: J
authors.lastname: Bauernfeind
authors.forename: J
authors.initials: J
authors.lastname: Krska
mesh_terms: D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D005822:Genetic Vectors; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D010957:Plasmids
chemical_list: C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C063842:dnaK protein, E coli