Binds RuBisCO small and large subunits and is implicated in the assembly of the enzyme oligomer. Involved in protein assisted folding. Required for proper chloroplast development. Part of the Cpn60 complex composed of 7 alpha and 7 beta subunits. This complex shows ATPase activity. The Cpn60 complex interacts with the Cpn10 complex. Expressed in leaves, stems, siliques and flowers. Up-regulated by light. Embryos are albino, can germinate but are unable to produce viable seedlings. Assisted protein folding requires ATP hydrolysis, but not K(+) ions. Belongs to the chaperonin (HSP60) family.