title: DnaK, DnaJ and GrpE form a cellular chaperone machinery capable of repairing heat-induced protein damage.
abstract: Members of the conserved Hsp70 chaperone family are assumed to constitute a main cellular system for the prevention and the amelioration of stress-induced protein damage, though little direct evidence exists for this function. We investigated the roles of the DnaK (Hsp70), DnaJ and GrpE chaperones of Escherichia coli in prevention and repair of thermally induced protein damage using firefly luciferase as a test substrate. In vivo, luciferase was rapidly inactivated at 42 degrees C, but was efficiently reactivated to 50% of its initial activity during subsequent incubation at 30 degrees C. DnaK, DnaJ and GrpE did not prevent luciferase inactivation, but were essential for its reactivation. In vitro, reactivation of heat-inactivated luciferase to 80% of its initial activity required the combined activity of DnaK, DnaJ and GrpE as well as ATP, but not GroEL and GroES. DnaJ associated with denatured luciferase, targeted DnaK to the substrate and co-operated with DnaK to prevent luciferase aggregation at 42 degrees C, an activity that was required for subsequent reactivation. The protein repair function of DnaK, GrpE and, in particular, DnaJ is likely to be part of the role of these proteins in regulation of the heat shock response.
authors.affiliation: Zentrum für Molekulare Biologie, Universität Heidelberg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Schröder
authors.forename: T
authors.initials: T
authors.lastname: Langer
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
authors.forename: B
authors.initials: B
authors.lastname: Bukau
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018833:Chaperonins; D004789:Enzyme Activation; D004793:Enzyme Reactivators / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D008156:Luciferases / Q000378:metabolism*; D005810:Multigene Family; D011489:Protein Denaturation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C494635:DnaJ protein, E coli; D004793:Enzyme Reactivators; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D011506:Proteins; D011994:Recombinant Proteins; D008156:Luciferases; D018833:Chaperonins; C063842:dnaK protein, E coli