STRUCTURE AND FUNCTION IN GROEL-MEDIATED PROTEIN-FOLDING

Recent structural and biochemical investigations have come together to allow a better understanding of the mechanism of chaperonin (GroEL, H sp60)-mediated protein folding, the final step in the accurate express ion of genetic information. Major, asymmetric conformational changes i n the GroEL double toroid accompany binding of ATP and the cochaperoni n GroES. When a nonnative polypeptide, bound to one of the GroEL rings , is encapsulated by GroES to form a cis ternary complex, these change s drive the polypeptide into the sequestered cavity and initiate its f olding. ATP hydrolysis in the cis ring primes release of the products, and ATP binding in the trans ring then disrupts the cis complex. This process allows the polypeptide to achieve its final native state, if folding was completed, or to recycle to another chaperonin molecule, i f the folding process did not result in a form committed to the native state.