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HSP27 multimerization mediated by phosphorylation-sensitive intermolecular interactions at the amino terminus.
H Lambert1, S J Charette, A F Bernier
1Centre de recherche en cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Québec, Québec G1R 2J6, Canada.
The Journal of Biological Chemistry
|March 27, 1999
Summary
Heat shock protein 27 (HSP27) forms multimers, shifting to dimers upon Ser90 phosphorylation. This structural change, mediated by N-terminal domains, influences HSP27 complex formation and function.
Area of Science:
- Molecular Biology
- Protein Biochemistry
- Cellular Stress Response
Background:
- Heat shock protein 27 (HSP27) exhibits distinct biochemical activities based on its molecular complex size.
- Understanding HSP27's structural dynamics is crucial for elucidating its cellular roles.
Purpose of the Study:
- To investigate the multimeric state of Chinese hamster HSP27.
- To determine the role of phosphorylation, specifically at Ser15 and Ser90, in regulating HSP27 complex structure.
- To identify domains responsible for HSP27 intermolecular interactions and phosphorylation-dependent structural changes.
Main Methods:
- Glycerol gradient ultracentrifugation and chemical cross-linking to analyze HSP27 complex sizes.
- Yeast two-hybrid system to identify protein interaction domains.
- Site-directed mutagenesis (Ser90Ala, Ser15Ala) and domain deletion to assess functional impact.
Main Results:
- Chinese hamster HSP27 exists as homotypic multimers (dimers to 700-kDa oligomers).
- Arsenite-induced phosphorylation at Ser90 caused a shift from oligomers to dimers; Ser90 phosphorylation is necessary and sufficient for this change.
- The C-terminal alpha-crystallin domain mediates stable dimer formation, while the N-terminal domain mediates phosphorylation-sensitive multimerization.
Conclusions:
- HSP27 forms stable dimers via its alpha-crystallin domain.
- The N-terminal domain, sensitive to Ser90 phosphorylation, drives multimerization of these dimers.
- Phosphorylation-dependent structural transitions regulate HSP27 complex formation and potentially its function.