title: Hsp70 proteins bind Hsp100 regulatory M domains to activate AAA+ disaggregase at aggregate surfaces.
abstract: Bacteria, fungi and plants rescue aggregated proteins using a powerful bichaperone system composed of an Hsp70 chaperone and an Hsp100 AAA+ disaggregase. In Escherichia coli, the Hsp70 chaperone DnaK binds aggregates and targets the disaggregase ClpB to the substrate. ClpB hexamers use ATP to thread substrate polypeptides through the central pore, driving disaggregation. How ClpB finds DnaK and regulates threading remains unclear. To dissect the disaggregation mechanism, we separated these steps using primarily chimeric ClpB-ClpV constructs that directly recognize alternative substrates, thereby obviating DnaK involvement. We show that ClpB has low intrinsic disaggregation activity that is normally repressed by the ClpB middle (M) domain. In the presence of aggregate, DnaK directly binds M-domain motif 2, increasing ClpB ATPase activity to unleash high ClpB threading power. Our results uncover a new function for Hsp70: the coupling of substrate targeting to AAA+ chaperone activation at aggregate surfaces.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Seyffer
authors.forename: Eva
authors.initials: E
authors.lastname: Kummer
authors.forename: Yuki
authors.initials: Y
authors.lastname: Oguchi
authors.forename: Juliane
authors.initials: J
authors.lastname: Winkler
authors.forename: Mohit
authors.initials: M
authors.lastname: Kumar
authors.forename: Regina
authors.initials: R
authors.lastname: Zahn
authors.forename: Victor
authors.initials: V
authors.lastname: Sourjik
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.forename: Axel
authors.initials: A
authors.lastname: Mogk
mesh_terms: D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D018840:HSP70 Heat-Shock Proteins