title: Thermosensor action of GrpE. The DnaK chaperone system at heat shock temperatures.
abstract: Temperature directly controls functional properties of the DnaK/DnaJ/GrpE chaperone system. The rate of the high to low affinity conversion of DnaK shows a non-Arrhenius temperature dependence and above approximately 40 degrees C even decreases. In the same temperature range, the ADP/ATP exchange factor GrpE undergoes an extensive, fully reversible thermal transition (Grimshaw, J. P. A., Jelesarov, I., Schönfeld, H. J., and Christen, P. (2001) J. Biol. Chem. 276, 6098-6104). To show that this transition underlies the thermal regulation of the chaperone system, we introduced an intersubunit disulfide bond into the paired long helices of the GrpE dimer. The transition was absent in disulfide-linked GrpE R40C but was restored by reduction. With disulfide-stabilized GrpE, the rate of ADP/ATP exchange and conversion of DnaK from its ADP-liganded high affinity R state to the ATP-liganded low affinity T state continuously increased with increasing temperature. With reduced GrpE R40C, the conversion became slower at temperatures >40 degrees C, as observed with wild-type GrpE. Thus, the long helix pair in the GrpE dimer acts as a thermosensor that, by decreasing its ADP/ATP exchange activity, induces a shift of the DnaK.substrate complexes toward the high affinity R state and in this way adapts the DnaK/DnaJ/GrpE system to heat shock conditions.
authors.affiliation: Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: John P A
authors.initials: JP
authors.lastname: Grimshaw
authors.forename: Ilian
authors.initials: I
authors.lastname: Jelesarov
authors.forename: Rahel K
authors.initials: RK
authors.lastname: Siegenthaler
authors.forename: Philipp
authors.initials: P
authors.lastname: Christen
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature; D007700:Kinetics; D013058:Mass Spectrometry; D016297:Mutagenesis, Site-Directed; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C063842:dnaK protein, E coli