title: Heat shock protein 90 from Escherichia coli collaborates with the DnaK chaperone system in client protein remodeling.
abstract: Molecular chaperones are proteins that assist the folding, unfolding, and remodeling of other proteins. In eukaryotes, heat shock protein 90 (Hsp90) proteins are essential ATP-dependent molecular chaperones that remodel and activate hundreds of client proteins with the assistance of cochaperones. In Escherichia coli, the activity of the Hsp90 homolog, HtpG, has remained elusive. To explore the mechanism of action of E. coli Hsp90, we used in vitro protein reactivation assays. We found that E. coli Hsp90 promotes reactivation of heat-inactivated luciferase in a reaction that requires the prokaryotic Hsp70 chaperone system, known as the DnaK system. An Hsp90 ATPase inhibitor, geldanamycin, inhibits luciferase reactivation demonstrating the importance of the ATP-dependent chaperone activity of E. coli Hsp90 during client protein remodeling. Reactivation also depends upon the ATP-dependent chaperone activity of the DnaK system. Our results suggest that the DnaK system acts first on the client protein, and then E. coli Hsp90 and the DnaK system collaborate synergistically to complete remodeling of the client protein. Results indicate that E. coli Hsp90 and DnaK interact in vivo and in vitro, providing additional evidence to suggest that E. coli Hsp90 and the DnaK system function together.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892,, USA.
authors.forename: Olivier
authors.initials: O
authors.lastname: Genest
authors.forename: Joel R
authors.initials: JR
authors.lastname: Hoskins
authors.forename: Jodi L
authors.initials: JL
authors.lastname: Camberg
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Doyle
authors.forename: Sue
authors.initials: S
authors.lastname: Wickner
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000502:physiology*; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000502:physiology*; D008156:Luciferases / Q000737:chemistry; D008958:Models, Molecular; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D020673:Protein Renaturation; D020836:Protein Structure, Quaternary
chemical_list: D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D008156:Luciferases; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli