Mechanism of regulation of Hsp70 chaperones by DnaJ cochaperones

Citation
T. Laufen et al., Mechanism of regulation of Hsp70 chaperones by DnaJ cochaperones, P NAS US, 96(10), 1999, pp. 5452-5457
Citations number
39
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN journal
00278424 → ACNP
Volume
96
Issue
10
Year of publication
1999
Pages
5452 - 5457
Database
ISI
SICI code
0027-8424(19990511)96:10<5452:MOROHC>2.0.ZU;2-A
Abstract
Hsp70 chaperones assist a large variety of protein folding processes within the entire lifespan of proteins. Central to these activities is the regula tion of Hsp70 bg DnaJ cochaperones. DnaJ stimulates Hsp70 to hydrolyze ATP, a key step that closes its substrate-binding cavity and thus allows stable binding of substrate. We show that DnaJ stimulates ATP hydrolysis by Esche richia coli Hsp70, DnaK, very efficiently to >1000-fold, but only if presen t at high (micromolar) concentration, In contrast, the chaperone activity o f DnaK in luciferase refolding was maximal at several hundredfold lower con centration of DnaJ, However, DnaJ was capable of maximally stimulating the DnaK ATPase even at this low concentration, provided that protein substrate was present, indicating synergistic action of DnaJ and substrate. Peptide substrates were poorly effective in this synergistic action. DnaJ action re quired binding of protein substrates to the central hydrophobic pocket of t he substrate-binding cavity of DnaK as evidenced by the reduced ability of DnaJ to stimulate ATP hydrolysis by a DnaK mutant with defects in substrate binding. At high concentrations, DnaJ itself served as substrate for DnaK in a process considered to be unphysiological, Mutant analysis furthermore revealed that DnaJ-mediated stimulation of ATP hydrolysis requires communic ation between the ATPase and substrate-binding domains of DnaK. This mechan ism thus allows DnaJ to tightly couple ATP hydrolysis by DnaK with substrat e binding and to avoid jamming of the DnaK chaperone with peptides. It prob ably is conserved among Hsp70 family members and is proposed to account for their functional diversity.