GroEL under heat-shock. Switching from a folding to a storing function

• Published in: The Journal of biological chemistry 1998-12, Vol.273 (49), p.32587-32594
• Main Authors: Llorca, O, Galán, A, Carrascosa, J L, Muga, A, Valpuesta, J M
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Chaperonin 60 - metabolism; Escherichia coli; Escherichia coli - metabolism; Heat-Shock Response; Hot Temperature; Protein Folding
• ISSN: 0021-9258
• DOI: 10.1074/jbc.273.49.32587

Chaperonin GroEL from Escherichia coli, together with its cochaperonin GroES, are proteins involved in assisting the folding of polypeptides. GroEL is a tetradecamer composed of two heptameric rings, which enclose a cavity where folding takes place through multiple cycles of substrate and GroES binding and release. GroEL and GroES are also heat-shock proteins, their synthesis being increased during heat-shock conditions to help the cell coping with the thermal stress. Our results suggest that, as the temperature increases, GroEL decreases its protein folding activity and starts acting as a "protein store." The molecular basis of this behavior is the loss of inter-ring signaling, which slows down GroES liberation from GroEL and therefore the release of the unfolded protein from the GroEL cavity. This behavior is reversible, and after heat-shock, GroEL reverts to its normal function. This might have a physiological meaning, since under thermal stress conditions, it may be inefficient for the cell to fold thermounstable proteins that are prone to denaturation.