title: Dimeric trigger factor stably binds folding-competent intermediates and cooperates with the DnaK-DnaJ-GrpE chaperone system to allow refolding.
abstract: Trigger factor (TF) is the first chaperone encountered by the nascent chain in bacteria and forms a stoichiometric complex with the ribosome. However, the functional significance of the high cytosolic concentration of uncomplexed TF, the majority of which is dimeric, is unknown. To gain insight into TF function, we investigated the TF concentration dependence of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) reactivation yield in the presence and absence of the DnaK-DnaJ-GrpE chaperone system in vitro. Cross-linking results indicate that the observed decrease in the reactivation yield of GAPDH at high concentrations of TF is due to the formation of a stable complex between TF dimer and GAPDH intermediates. In the absence of TF, or at low TF concentrations, the DnaK-DnaJ-GrpE chaperone system had negligible effect on the GAPDH refolding yield. However, GAPDH intermediates bound and held by dimeric TF could be specifically rescued by the DnaK-DnaJ-GrpE chaperone system in an ATP-dependent manner. This indicates the potential of TF, in its dimeric form, to act as a binding chaperone, maintaining non-native proteins in a refolding competent conformation and cooperating with downstream molecular chaperones to facilitate post-translational or post-stress protein folding.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Chuan-Peng
authors.initials: CP
authors.lastname: Liu
authors.forename: Sarah
authors.initials: S
authors.lastname: Perrett
authors.forename: Jun-Mei
authors.initials: JM
authors.lastname: Zhou
mesh_terms: D000818:Animals; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D046912:Multiprotein Complexes; D019696:Peptidylprolyl Isomerase / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D020673:Protein Renaturation; D020836:Protein Structure, Quaternary
chemical_list: 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; D046912:Multiprotein Complexes; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C063842:dnaK protein, E coli; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase