Describe the mechanism by which the bacterial chaperonin GroEL promotes protein folding.

The bacterial chaperonin GroEL forms a barrel-shaped complex of 14 identical subunits.A partially folded or misfolded polypeptide is inserted into the GroEL barrel,where it binds to the inner wall and folds into its native conformation.In an ATP-dependent step,the GroEL barrel expands to a more open state,which results in release of the folded protein.