title: Real time kinetics of the DnaK/DnaJ/GrpE molecular chaperone machine action.
abstract: Applying stopped-flow fluorescence spectroscopy for measuring conformational changes of the DnaK molecular chaperone (bacterial Hsp70 homologue) and its binding to target peptide, we found that after ATP hydrolysis, DnaK is converted to the DnaK*(ADP) conformation, which possesses limited affinity for peptide substrates and the GrpE cochaperone but efficiently binds the DnaJ chaperone. In the presence of DnaJ (bacterial Hsp40 homologue), the DnaK*(ADP) form is converted back to the DnaK conformation, and the resulting DnaJ-DnaK(ADP) complex binds to peptide substrates more tightly. Formation of the DnaJ(substrate-DnaK(ADP)) complex is a rate-limiting reaction. The presence of GrpE and ATP hydrolysis promotes the fast release of the peptide substrate from the chaperone complex and converts DnaK to the DnaK*(ADP) conformation. We conclude that in the presence of DnaJ and GrpE, the binding-release cycle of DnaK is stoichiometrically coupled to the adenosine triphosphatase activity of DnaK.
authors.affiliation: Division of Biophysics, Department of Molecular Biology, University of Gdansk, Poland.
authors.forename: B
authors.initials: B
authors.lastname: Banecki
authors.forename: M
authors.initials: M
authors.lastname: Zylicz
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; C494635:DnaJ protein, E coli; 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; D018832:Molecular Chaperones; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli