Journal Article

An S/T motif controls reversible oligomerization of the Hsp40 chaperone DNAJB6b through subtle reorganization of a β sheet backbone

Karamanos, Theodoros K., Tugarinov, Vitali, Clore, G. Marius

2020

Overview

Chaperone oligomerization is often a key aspect of their function. Irrespective of whether chaperone oligomers act as reservoirs for active monomers or exhibit a chaperoning function themselves, understanding the mechanism of oligomerization will further our understanding of how chaperones maintain the proteome. Here, we focus on the class-II Hsp40, human DNAJB6b, a highly efficient inhibitor of protein self-assembly in vivo and in vitro that forms functional oligomers. Using single-quantum methyl-based relaxation dispersion NMR methods we identify critical residues for DNAJB6b oligomerization in its C-terminal domain (CTD). Detailed solution NMR studies on the structure of the CTD showed that a serine/threonine-rich stretch causes a backbone twist in the N-terminal β strand, stabilizing the monomeric form. Quantitative analysis of an array of NMR relaxation-based experiments (including Carr–Purcell–Meiboom–Gill relaxation dispersion, off-resonance R 1ρ profiles, lifetime line broadening, and exchange-induced shifts) on the CTD of both wild type and a point mutant (T142A) within the S/T region of the first β strand delineates the kinetics of the interconversion between the major twisted-monomeric conformation and a more regular β strand configuration in an excited-state dimer, as well as exchange of both monomer and dimer species with high-molecular-weight oligomers. These data provide insights into the molecular origins of DNAJB6b oligomerization. Further, the results reported here have implications for the design of β sheet proteins with tunable self-assembling properties and pave the way to an atomic-level understanding of amyloid inhibition.

• Publisher: National Academy of Sciences
• Subject: Amino Acid Motifs / Amino Acid Sequence / Amyloid / Backbone / Biological Sciences / Biophysics and Computational Biology / Chaperones / Dimers / Dispersion / Exchanging / HSP40 Heat-Shock Proteins - chemistry / HSP40 Heat-Shock Proteins - metabolism / Hsp40 protein / Kinetics / Line broadening / Models, Molecular / Monomers / NMR / Nuclear magnetic resonance / Oligomerization / Oligomers / Physical Sciences / Protein Binding / Protein Conformation / Protein Conformation, beta-Strand / Protein Interaction Domains and Motifs / Protein Multimerization / Proteins / Proteomes / Self-assembly / Serine / Threonine