![]() Rudiger97a].Heat shock protein 90 (HSP90) is a molecular chaperone that is conserved from bacteria to humans and facilitates the maturation of substrates (or clients) that are involved in many different cellular pathways. DnaK binds to a consensus motif consisting of a hydrophobic core of 4-5 residues (most commonly Leu) flanked by basic residues Trigger factor to chaperone de novo protein foldingĭnaK binds with the highest affinity to short hydrophobic peptide segments in extended conformation DnaK-DnaJ-GrpE acts cooperatively withĬlpB to mediate disaggregation and refolding of thermolabile proteins DnaK, DnaJ and GrpE plus ATP are able to convert misfolded luciferase into an unfolded intermediate which spontaneously refolds into its native configuration after release from the chaperone The presence of DnaJ and GrpE stimulates the ATPase activity of DnaK in vitroĭnaK, DnaJ, GrpE and ATP are required to mediate the efficient folding of misfolded luciferase in vitro The co-chaperones, GrpE and DnaJ act to control the flux of substrate through the SBD of DnaK by regulating the nucleotide bound state (reviews: Purified DnaK possesses weak ATPase activity and an autophosphorylating activity The molecular mechanism underpinning interdomain allostery in DnaK is the subject of considerable research In turn, substrate binding results in stimulation of the ATPase activity of the NBD The NBD regulates the substrate affinity of the SBD in a nucleotide dependent manner - alternating between an ATP bound state (the T-state) with low affinity/fast exchange of substrate and an ADP bound state (the R-state) with high affinity/low exchange rate of substrate. DnaK functions are mediated by interdomain allostery. Stevens03] and a 10kDa subdomain of α-helical structure (residues 510-638) , a 17 kDa substrate-binding domain (SBD residues 390-600) The DnaK chaperone system is also essential for bacteriophage λ DNA replication and is involved in the formation and disassembly of the initiation complex at the viral origin of replication ori-λĭnaK consists of an N-terminal nucleotide binding domain (NBD residues 1-370) Σ 32, the primary sigma factor controlling heat shock response during log phase growth (reviewed inĪrsene00]). The DnaK system contributes to control of the heat shock response in E. The chaperone action of DnaK is powered by ATP hydrolysis and is assisted by partner chaperones DnaK assists in a number of cytoplasmic cellular processes including folding of nascent polypeptide chains GO:0005886 - plasma membrane ĭnaK is a Hsp70 (heat shock 70 kDa) chaperone in E. GO:0044183 - protein binding involved in protein folding GO:0051085 - chaperone mediated protein folding requiring cofactor ![]() GO:0043241 - protein complex disassembly GO:0034620 - cellular response to unfolded protein Subunit of DnaK-DnaJ-GrpE chaperone system: chaperone protein DnaK GO:0042803 - protein homodimerization activity GO:0016989 - sigma factor antagonist activity GO:0015035 - protein disulfide oxidoreductase activity GO:0003756 - protein disulfide isomerase activity GO:0070389 - chaperone cofactor-dependent protein refolding Subunit of DnaK-DnaJ-GrpE chaperone system: DnaJ monomer ![]()
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