Assembly of chaperonin complexes.

Chaperonins are a subclass of molecular chaperones that assist both the folding of newly synthesized proteins and the maintenance of proteins in a folded state during periods of stress. The best studied members of this family are the type I chaperonins, occurring in bacteria and evolutionarily derived organelles. Type II chaperonins occur in archaea and the eukaryotic cytosol. An intriguing question pertains to the mechanism by which chaperonins themselves are folded and assembled into functional oligomers. The available evidence for the assembly/disassembly of type I and II chaperonins points to a process that is highly cooperative and suggests a prominent role for nucleotides. Interestingly, the intracellular assembly of type I chaperonins appears to be a chaperone-dependent process itself and requires functional preformed chaperonin complexes.