title: Mechanism of the targeting action of DnaJ in the DnaK molecular chaperone system.
abstract: In the DnaK (Hsp70) molecular chaperone system of Escherichia coli, the substrate polypeptide is fed into the chaperone cycle by association with the fast-binding, ATP-liganded form of the DnaK. The substrate binding properties of DnaK are controlled by its two cochaperones DnaJ (Hsp40) and GrpE. DnaJ stimulates the hydrolysis of DnaK-bound ATP, and GrpE accelerates ADP/ATP exchange. DnaJ has been described as targeting the substrate to DnaK, a concept that has remained rather obscure. Based on binding experiments with peptides and polypeptides we propose here a novel mechanism for the targeting action of DnaJ: ATP.DnaK and DnaJ with its substrate-binding domain bind to different segments of one and the same polypeptide chain forming (ATP.DnaK)m.substrate.DnaJn complexes; in these ternary complexes efficient cis-interaction of the J-domain of DnaJ with DnaK is favored by their propinquity and triggers the hydrolysis of DnaK-bound ATP, converting DnaK to its ADP-liganded high affinity state and thus locking it onto the substrate polypeptide.
authors.affiliation: Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Wanjiang
authors.initials: W
authors.lastname: Han
authors.forename: Philipp
authors.initials: P
authors.lastname: Christen
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000494:pharmacology; D001667:Binding, Competitive; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism / Q000494:pharmacology*; D006868:Hydrolysis; D008156:Luciferases / Q000737:chemistry / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D013884:Thiosulfate Sulfurtransferase / Q000737:chemistry / Q000494:pharmacology
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; D010446:Peptide Fragments; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008156:Luciferases; D013884:Thiosulfate Sulfurtransferase; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli