Protein disaggregation by the AAA+ chaperone ClpB involves partial threading of looped polypeptide segments.
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.
Haslberger
Tobias
T
Zentrum für Molekulare Biologie Heidelberg, DKFZ-ZMBH Alliance, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany.
Zdanowicz
Agnieszka
A
Brand
Ingo
I
Kirstein
Janine
J
Turgay
Kürsad
K
Mogk
Axel
A
Bukau
Bernd
B
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
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