Binds RuBisCO small and large subunits and is implicated in the assembly of the enzyme oligomer. Involved in protein assisted folding. Required for proper plastid division. Part of the Cpn60 complex composed of 7 alpha and 7 beta subunits. Can also form a complex composed of 14 beta subunits only. Both complexes show ATPase activity. The Cpn60 complex interacts with the Cpn10 complex. Interacts with RAB during heat stress. Expressed in leaves, stems, petioles and flowers. Up-regulated by light. Down-regulated by wounding. Not induced by heat. Normal germination, but chloroplast-division defect and late dwarf phenotype. Lesion formation on leaves when grown under short-day conditions. Cpn60B1 and cpn60B2 double mutant produces small albino seedlings. Assisted protein folding requires ATP hydrolysis, but not K(+) ions. Belongs to the chaperonin (HSP60) family.