It takes a dimer to tango: Oligomeric small heat shock proteins dissociate to capture substrate
| Autor: | Justin L. P. Benesch, Georg K. A. Hochberg, Matteo T. Degiacomi, Indu Santhanagopalan, Elizabeth Vierling, Dale A. Shepherd |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Models
Molecular 0301 basic medicine Dimer Protein design Biochemistry 03 medical and health sciences chemistry.chemical_compound Malate Dehydrogenase Disulfides Protein Structure Quaternary Molecular Biology Protein secondary structure Heat-Shock Proteins biology fungi Cell Biology Protein engineering 030104 developmental biology Monomer chemistry Covalent bond Chaperone (protein) Mutation Protein Structure and Folding biology.protein Biophysics Protein folding Protein Multimerization Protein Binding |
| Zdroj: | J Biol Chem Journal of biological chemistry, 2018, Vol.293(51), pp.19511-19521 [Peer Reviewed Journal] |
| ISSN: | 1083-351X 0021-9258 |
| Popis: | Small heat-shock proteins (sHsps) are ubiquitous molecular chaperones, and sHsp mutations or altered expression are linked to multiple human disease states. sHsp monomers assemble into large oligomers with dimeric substructure, and the dynamics of sHsp oligomers has led to major questions about the form that captures substrate, a critical aspect of their mechanism of action. We show here that substructural dimers of two plant dodecameric sHsps, Ta16.9 and homologous Ps18.1, are functional units in the initial encounter with unfolding substrate. We introduced inter-polypeptide disulfide bonds at the two dodecameric interfaces, dimeric and nondimeric, to restrict how their assemblies can dissociate. When disulfide-bonded at the nondimeric interface, mutants of Ta16.9 and Ps18.1 (Ta(CT-ACD) and Ps(CT-ACD)) were inactive but, when reduced, had WT-like chaperone activity, demonstrating that dissociation at nondimeric interfaces is essential for sHsp activity. Moreover, the size of the Ta(CT-ACD) and Ps(CT-ACD) covalent unit defined a new tetrahedral geometry for these sHsps, different from that observed in the Ta16.9 X-ray structure. Importantly, oxidized Ta(dimer) (disulfide bonded at the dimeric interface) exhibited greatly enhanced ability to protect substrate, indicating that strengthening the dimeric interface increases chaperone efficiency. Temperature-induced size and secondary structure changes revealed that folded sHsp dimers interact with substrate and that dimer stability affects chaperone efficiency. These results yield a model in which sHsp dimers capture substrate before assembly into larger, heterogeneous sHsp–substrate complexes for substrate refolding or degradation, and suggest that tuning the strength of the dimer interface can be used to engineer sHsp chaperone efficiency. |
| Databáze: | OpenAIRE |
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