GROES BINDING REGULATES GROEL CHAPERONIN ACTIVITY UNDER HEAT-SHOCK

Chaperonins GroEL(14) and GroES(7) are heat-shock proteins implicated in the molecular response to stress. Protein fluorescence, crosslinkin g and kinetic analysis revealed that the bond between the two otherwis e thermoresistant oligomers is regulated by temperature. As temperatur e increased, the affinity of GroES(7) and the release of bound protein s from the chaperonin concomitantly decreased. After heat shock, GroES (7) rebinding to GroEL(14) and GroEL(14)GroES(7) particles correlated with the restoration of optimal protein folding/release activity. Chap eronins thus behave as a molecular thermometer which can inhibit the r elease of aggregation-prone proteins during heat shock and restore pro tein folding and release after heat shock. (C) 1997 Federation of Euro pean Biochemical Societies.