GroES binding regulates GroEL chaperonin activity under heat shock

Chaperonins GroEL₁₄ and GroES₇ are heat-shock proteins implicated in the molecular response to stress. Protein fluorescence, crosslinking and kinetic analysis revealed that the bond between the two otherwise thermoresistant oligomers is regulated by temperature. As temperature increased, the affinity of GroES₇ and the release of bound proteins from the chaperonin concomitantly decreased. After heat shock, GroES₇ rebinding to GroEL₁₄ and GroEL₁₄GroES₇ particles correlated with the restoration of optimal protein folding/release activity. Chaperonins thus behave as a molecular thermometer which can inhibit the release of aggregation-prone proteins during heat shock and restore protein folding and release after heat shock.