Conformational changes in the chaperonin GroEL: New insights into the allosteric mechanism

Conformational changes are known to play a crucial role in the function of the bacterial GroE chaperonin system. Here, results are presented from an e ssential dynamics analysis of known experimental structures and from comput er simulations of GroEL using the CONCOORD method. The results indicate a p ossible direct form of inter-ring communication associated with internal fl uctuations in the nucleotide-binding domains upon nucleotide and GroES bind ing that are involved in the allosteric mechanism of GroEL. At the level of conformational transitions in entire GroEL rings, nucleotide-induced struc tural changes were found to be distinct and in principle uncoupled from cha nges occurring upon GroES binding. However, a coupling is found between nuc leotide-induced conformational changes and GroES-mediated transitions, but only in simulations of GroEL double rings, and not in simulations of single rings. This provides another explanation for the fact that GroEL functions a double ring system. (C) 1999 Academic Press.