Linked Life Data

10194333

Source:http://linkedlifedata.com/resource/pubmed/id/10194333

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
1999-4-21
pubmed:abstractText
Most, if not all, of the cellular functions of Hsp70 proteins require the assistance of a DnaJ homologue, which accelerates the weak intrinsic ATPase activity of Hsp70 and serves as a specificity factor by binding and targeting specific polypeptide substrates for Hsp70 action. We have used pre-steady-state kinetics to investigate the interaction of the Escherichia coli DnaJ and DnaK proteins, and the effects of DnaJ on the ATPase reaction of DnaK. DnaJ accelerates hydrolysis of ATP by DnaK to such an extent that ATP binding by DnaK becomes rate-limiting for hydrolysis. At high concentrations of DnaK under single-turnover conditions, the rate-limiting step is a first-order process, apparently a change of DnaK conformation, that accompanies ATP binding and proceeds at 12-15 min-1 at 25 degrees C and 1-1.5 min-1 at 5 degrees C. By prebinding ATP to DnaK and subsequently adding DnaJ, the effects of this slow step may be bypassed, and the maximal rate-enhancement of DnaJ on the hydrolysis step is approximately 15 000-fold at 5 degrees C. The interaction of DnaJ with DnaK.ATP is likely a rapid equilibrium relative to ATP hydrolysis, and is relatively weak, with a KD of approximately 20 microM at 5 degrees C, and weaker still at 25 degrees C. In the presence of saturating DnaJ, the maximal rate of ATP hydrolysis by DnaK is similar to previously reported rates for peptide release from DnaK.ATP. This suggests that when DnaK encounters a DnaJ-bound polypeptide or protein complex, a significant fraction of such events result in ATP hydrolysis by DnaK and concomitant capture of the polypeptide substrate in a tight complex with DnaK.ADP. Furthermore, a broadly applicable kinetic mechanism for DnaJ-mediated specificity of Hsp70 action arises from these observations, in which the specificity arises largely from the acceleration of the hydrolysis step itself, rather than by DnaJ-dependent modulation of the affinity of Hsp70 for substrate polypeptides.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4165-76
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed-meshheading:10194333-Adenosine Triphosphatases, pubmed-meshheading:10194333-Adenosine Triphosphate, pubmed-meshheading:10194333-Bacterial Proteins, pubmed-meshheading:10194333-Chlorides, pubmed-meshheading:10194333-Cold Temperature, pubmed-meshheading:10194333-Enzyme Activation, pubmed-meshheading:10194333-Escherichia coli Proteins, pubmed-meshheading:10194333-HSP40 Heat-Shock Proteins, pubmed-meshheading:10194333-HSP70 Heat-Shock Proteins, pubmed-meshheading:10194333-Heat-Shock Proteins, pubmed-meshheading:10194333-Hydrolysis, pubmed-meshheading:10194333-Kinetics, pubmed-meshheading:10194333-Models, Biological, pubmed-meshheading:10194333-Models, Chemical, pubmed-meshheading:10194333-Peptides, pubmed-meshheading:10194333-Protein Binding, pubmed-meshheading:10194333-Substrate Specificity
pubmed:year
1999
pubmed:articleTitle
DnaJ dramatically stimulates ATP hydrolysis by DnaK: insight into targeting of Hsp70 proteins to polypeptide substrates.
pubmed:affiliation
Department of Biochemistry, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.