title: Protein disaggregation by the AAA+ chaperone ClpB involves partial threading of looped polypeptide segments.
abstract: The ring-forming AAA+ chaperone ClpB cooperates with the DnaK chaperone system to reactivate aggregated proteins. With the assistance of DnaK, ClpB extracts unfolded polypeptides from aggregates via substrate threading through its central channel. Here we analyze the processing of mixed aggregates consisting of protein fusions of misfolded and native domains. ClpB-DnaK reactivated all aggregated fusion proteins with similar efficiency, without unfolding native domains, demonstrating that partial threading of the misfolded moiety is sufficient to solubilize aggregates. Reactivation by ClpB-DnaK occurred even when two stably folded domains flanked the aggregated moiety, indicating threading of internal substrate segments. In contrast with the related AAA+ chaperone ClpC, ClpB lacks a robust unfolding activity, enabling it to sense the conformational state of substrates. ClpB rings are highly unstable, which may facilitate dissociation from trapped substrates during threading.
authors.affiliation: Zentrum für Molekulare Biologie Heidelberg, DKFZ-ZMBH Alliance, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Haslberger
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Zdanowicz
authors.forename: Ingo
authors.initials: I
authors.lastname: Brand
authors.forename: Janine
authors.initials: J
authors.lastname: Kirstein
authors.forename: Kürsad
authors.initials: K
authors.lastname: Turgay
authors.forename: Axel
authors.initials: A
authors.lastname: Mogk
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
mesh_terms: D001426:Bacterial Proteins; D003001:Cloning, Molecular; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000502:physiology*; D018832:Molecular Chaperones; D017510:Protein Folding; D020673:Protein Renaturation
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D049071:Endopeptidase Clp; C063842:dnaK protein, E coli; C069775:ClpB protein, E coli