The Escherichia coli chaperonins GroEL and GroES facilitate protein folding in vivo and in vitro. However, the mechanism of action is not well understood. N-(5'Phosphoribosyl)anthranilate isomerase from E. coli (ePRAI), an alpha/Beta barrel protein, will be used as substrate for the chaperonin. The proposed project will address the following specific aspects of the activity of GroEL: 1) To determine if the chaperonin modifies the folding pathway of ePRAI. 2) To determine the role of ATP and GroES in the folding mechanism. 3) To determine at which stage of the folding pathway and what region of ePRAI interacts with GroEL.