Bound substrate polypeptides can generally stabilize the tetradecameric structure of Cpn60 and induce its reassembly from monomers.

We demonstrate that the previously observed stabilizing effect by the enzyme rhodanese of the oligomeric structure of Cpn60 is general and can be provided by six other proteins that can interact with Cpn60. All these substrate proteins, which include examples that are monomeric, as well as oligomeric polypeptides in their native states, were shown previously to be assisted in their refolding by the chaperonin. Strikingly, during the disassembly of Cpn60 in the presence of any of the substrate proteins, significant amounts of intermediates were detected. Furthermore, unfolded substrate proteins induce the reassembly of tetradecameric Cpn60 from monomers, and binding of each substrate protein stabilizes Cpn60 quaternary structure.