Mechanism of the targeting action of DnaJ in the DnaK molecular chaperone system.
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.
Han
Wanjiang
W
Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Christen
Philipp
P
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
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