title: Mutations in the interdomain linker region of DnaK abolish the chaperone action of the DnaK/DnaJ/GrpE system.
abstract: Hsp70s assist the folding of proteins in an ATP-dependent manner. DnaK, the Hsp70 of Escherichia coli, acts in concert with its co-chaperones DnaJ and GrpE. Amino acid substitutions (D388R and L391S/L392G) in the linker region between the ATPase and substrate-binding domain did not affect the functional domain coupling and oligomerization of DnaK. The intrinsic ATPase activity was enhanced up to 10-fold. However, the ATPase activity of DnaK L391S/L392G, if stimulated by DnaJ plus protein substrate, was five times lower than that of wild-type DnaK and DnaK D388R. This defect correlated with the complete loss of chaperone action in luciferase refolding. Apparently, the conserved leucine residues in the linker mediate the synergistic effects of DnaJ and protein substrate on ATPase activity, a function which might be essential for chaperone action.
authors.affiliation: Biochemisches Institut der Universität Zürich, Winterthurerstrasse 90, CH-8057, Zurich, Switzerland.
authors.forename: W
authors.initials: W
authors.lastname: Han
authors.forename: P
authors.initials: P
authors.lastname: Christen
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000378:metabolism*; D017124:Conserved Sequence / Q000502:physiology; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli