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. Purified 65 kDa antigen can elicit a strong delayed-type hypersensitivity reaction in experimental animals infected with Mycobacterium tuberculosis. This protein is one of the major immunoreactive proteins of the Mycobacteria. This antigen contains epitopes that are common to various species of Mycobacteria. Belongs to the chaperonin (HSP60) family.