Together with its co-chaperonin GroES, plays an essential role in assisting protein folding. The GroEL-GroES system forms a nano-cage that allows encapsulation of the non-native substrate proteins and provides a physical environment optimized to promote and accelerate protein folding. ATP + H2O + a folded polypeptide = ADP + phosphate + an unfolded polypeptide. Forms a cylinder of 14 subunits composed of two heptameric rings stacked back-to-back. Interacts with the co-chaperonin GroES. By NifA. Belongs to the chaperonin (HSP60) family.