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. Present in large cell variant (LCV) stage and small cell variant (SCV) stage (at protein level). LCVs are more metabolically active than SCVs. Belongs to the chaperonin (HSP60) family.