GroEL under heat-shock. Switching from a folding to a storing function.
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.
Llorca
O
O
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
Galán
A
A
Carrascosa
J L
JL
Muga
A
A
Valpuesta
J M
JM
D000251:Adenosine Triphosphatases / Q000378:metabolism; D018834:Chaperonin 60 / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D018869:Heat-Shock Response; D006358:Hot Temperature; D017510:Protein Folding
D018834:Chaperonin 60; D000251:Adenosine Triphosphatases