Hsp70 proteins bind Hsp100 regulatory M domains to activate AAA+ disaggregase at aggregate surfaces

• Published in: Nature structural & molecular biology Vol. 19; no. 12; pp. 1347 - 1355
• Main Authors: Seyffer, Fabian, Kummer, Eva, Oguchi, Yuki, Winkler, Juliane, Kumar, Mohit, Zahn, Regina, Sourjik, Victor, Bukau, Bernd, Mogk, Axel
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.12.2012; Nature Publishing Group
• Subjects: 631/337/470/1981; 631/337/470/2284; Aggregates; ATP; Biochemistry; Biological Microscopy; E coli; Enzymes; Escherichia coli; Genetic variation; HSP70 Heat-Shock Proteins - metabolism; Identification and classification; Life Sciences; Membrane Biology; Molecular biology; Molecular chaperones; Properties; Protein Binding; Protein folding; Protein Structure; Protein-protein interactions; Substrates; Substrates (Biochemistry); Germany
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.2442

DnaK targets protein aggregates to ClpB. New data show that DnaK also activates ClpB in a species-specific manner through direct interactions with the M domain of ClpB, stabilizing a derepressed state that increases the ATP hydrolysis and protein disaggregation activities of the chaperone. Also in this issue, Oguchi et al . show how the M domain of ClpB acts as a reversible toggle to regulate these activities. 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.