BINDING OF DEFINED REGIONS OF A POLYPEPTIDE TO GROEL AND ITS IMPLICATIONS FOR CHAPERONIN-MEDIATED PROTEIN-FOLDING

Unfolded rhodanese in a complex with the chaperonin GroEL was subjected to limited proteolysis. Sequence analysis indentified a GroEL-bound fragment of similar to 11,000 M(r) and a well defined fragment of similar to 7,000 M(r) from the two homologous domains df rhodanese. The shorter segment contains one hydrophobic and one amphiphilic alpha-helix mapping to the domain interface while the other fragment contains the homologous regions and an additional hydrophobic helix, Our results suggest a mechanism for the GroEL-mediated folding of rhodanese in which the domain-forming regions of the polypeptide are kept apart and are then released, perhaps sequentially, resulting in correct folding.