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GroEL under heat-shock. Switching from a folding to a storing function
O Llorca1, A Galán, J L Carrascosa
1Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
The Journal of Biological Chemistry
|November 26, 1998
Summary
As temperatures rise, Escherichia coli chaperonin GroEL (and its partner GroES) reduces protein folding activity, acting as a temporary protein store. This heat-shock response helps cells manage thermal stress by pausing folding of unstable proteins.
Area of Science:
- Molecular Biology
- Protein Folding
- Heat Shock Response
Background:
- Chaperonin GroEL and cochaperonin GroES from Escherichia coli assist polypeptide folding within a central cavity.
- GroEL/GroES function involves cycles of substrate and cochaperonin binding and release.
- Both proteins are heat-shock proteins, upregulated during thermal stress.
Purpose of the Study:
- To investigate the functional changes of GroEL at elevated temperatures.
- To understand the molecular mechanisms behind GroEL's altered behavior during heat shock.
- To explore the physiological relevance of GroEL's heat-induced modifications.
Main Methods:
- Studied the protein folding activity of GroEL at varying temperatures.
- Investigated the binding and release dynamics of GroES with GroEL.
- Analyzed the inter-ring signaling within the GroEL tetradecamer.
Main Results:
- GroEL's protein folding activity decreases as temperature increases.
- Elevated temperatures lead to reduced GroES release due to impaired inter-ring signaling.
- GroEL transitions from a folding facilitator to a "protein store" under heat stress.
Conclusions:
- GroEL's function shifts from active folding to protein sequestration at higher temperatures.
- Loss of inter-ring communication is the molecular basis for this functional change.
- This reversible behavior may be a cellular strategy to conserve energy by not folding thermolabile proteins during stress.