title: Action of the Hsp70 chaperone system observed with single proteins.
abstract: In Escherichia coli, the binding of non-native protein substrates to the Hsp70 chaperone DnaK is mediated by the co-chaperone DnaJ. DnaJ accelerates ATP hydrolysis on DnaK, by closing the peptide-binding cleft of DnaK. GrpE catalysed nucleotide exchange and ATP re-binding then lead to substrate release from DnaK, allowing folding. Here we refold immunoglobulin 27 (I27) to better understand how DnaJ-DnaK-GrpE chaperones cooperate. When DnaJ is present, I27 is less likely to misfold and more likely to fold, whereas the unfolded state remains unaffected. Thus, the 'holdase' DnaJ shows foldase behaviour. Misfolding of I27 is fully abrogated when DnaJ cooperates with DnaK, which stabilizes the unfolded state and increases the probability of folding. Addition of GrpE shifts the unfolded fraction of I27 to pre-chaperone levels. These insights reveal synergistic mechanisms within the evolutionary highly conserved Hsp70 system that prevent substrates from misfolding and promote their productive transition to the native state.
authors: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
authors: João M
authors: JM
authors: Nunes
authors: Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
authors: Manajit
authors: M
authors: Mayer-Hartl
authors: Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
authors: F Ulrich
authors: FU
authors: Hartl
authors: Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
authors: Daniel J
authors: DJ
authors: Müller
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D017209:Apoptosis; D001665:Binding Sites; D064211:Connectin / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry*; D006360:Heat-Shock Proteins / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D018625:Microscopy, Atomic Force; D018832:Molecular Chaperones / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization
chemical_list: D064211:Connectin; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C577285:TTN protein, human; D006046:Gold; D000255:Adenosine Triphosphate; C063842:dnaK protein, E coli