The Hsp40 J-domain Stimulates Hsp70 When Tethered by the Client to the ATPase Domain |
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| Authors: | B. Erin Horne Tingfeng Li Pierre Genevaux Costa Georgopoulos Samuel J. Landry |
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| Affiliation: | From the ‡Department of Biochemistry, Tulane University Health Sciences Center, New Orleans, Louisiana 70112.;the §Département de Microbiologie et Génétique Moléculaire, IBCG, CNRS Univeristé Paul Sabatier, Toulouse, 31062, France, and ;the ¶Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112–5650 |
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| Abstract: | The Escherichia coli Hsp40 DnaJ uses its J-domain (Jd) to couple ATP hydrolysis and client protein capture in Hsp70 DnaK. Fusion of the Jd to peptide p5 (as in Jdp5) dramatically increases the apparent affinity of the p5 moiety for DnaK in the presence of ATP, and Jdp5 stimulates ATP hydrolysis in DnaK by several orders of magnitude. NMR experiments with [15N]Jdp5 demonstrated that the peptide tethers the Jd to the ATPase domain. Thus, ATP hydrolysis and client protein binding in DnaK are coupled principally through the association of the client with DnaJ. Overexpression of a recombinant Jd was specifically toxic to cells that simultaneously expressed DnaK. No toxicity was observed when overexpressing Jdp5 or mutant Jd or when co-overexpressing the Jd and the nucleotide exchange factor GrpE. The results suggest that the Jd shifts DnaK to a client-bound form by stimulating the DnaK ATPase but only when the Jd is brought to DnaK by a client-Hsp40 complex. |
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| Keywords: | ATPases Chaperone Chaperonin Fluorescence Heat Shock Protein NMR |
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