Seems to function only as a co-chaperone, along with CPN60, and in certain cases is essential for the discharge of biologically active proteins from CPN60 (PubMed:17178727, PubMed:23057508). Required to activate the iron superoxide dismutases (FeSOD) (PubMed:23057508). Involved in abscisic acid (ABA) signaling, independently of its co-chaperone role. Acts as negative regulator of the CHLH-WRKY40 coupled ABA signaling pathway, downstream of CHLH and upstream of WRKY40. Homotetramer. Forms stable complexes with CPN60 in the presence of ATP (PubMed:10205903). Interacts with FSD1 (PubMed:23057508). Interacts with CLPT1 and CLPT2 (PubMed:25921872). Interacts with CHLH (PubMed:23783410, PubMed:10205903, PubMed:23057508, PubMed:25921872). Interacts with SPY (PubMed:34712252). Ubiquitous. Most abundant in leaves and inflorescence. Low levels found in roots. Induced by heat treatment. Belongs to the GroES chaperonin family.