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 heat shock under both nitrogen-fixing and nitrogen-supplemented growth conditions. Induced within 5 to 15 minutes of the start of heat stress, levels peak after 1 hour and expression continues throughout the period of heat stress. Belongs to the chaperonin (HSP60) family.