title: The DnaK chaperone modulates the heat shock response of Escherichia coli by binding to the sigma 32 transcription factor.
abstract: The heat shock response and the heat shock proteins have been conserved across evolution. In Escherichia coli, the heat shock response is positively regulated by the sigma 32 transcriptional factor and negatively regulated by a subset of the heat shock proteins themselves. In an effort to understand the regulation of the heat shock response, we have purified the sigma 32 polypeptide to homogeneity. During the purification procedure, we found that a large fraction of the overexpressed sigma 32 polypeptide copurified with the universally conserved DnaK heat shock protein (the prokaryotic equivalent of the 70-kDa heat shock protein, HSP70). Further experiments established that purified sigma 32 bound to DnaK and that this complex was disrupted in the presence of ATP. Consistent with the fact that dnaK756 mutant bacteria overexpress heat shock proteins at all temperatures, purified DnaK756 mutant protein did not appreciably bind to sigma 32.
authors.affiliation: Department of Cellular, Viral and Molecular Biology, University of Utah Medical Center, Salt Lake City 84132.
authors.forename: K
authors.initials: K
authors.lastname: Liberek
authors.forename: T P
authors.initials: TP
authors.lastname: Galitski
authors.forename: M
authors.initials: M
authors.lastname: Zylicz
authors.forename: C
authors.initials: C
authors.lastname: Georgopoulos
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006358:Hot Temperature; D046911:Macromolecular Substances; D008970:Molecular Weight; D011485:Protein Binding; D012808:Sigma Factor / Q000302:isolation & purification / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; C063842:dnaK protein, E coli