Molecular chaperone that assists in the folding or refolding of nascent or denatured proteins along with ATP hydrolysis (Probable). ATPase activity is highest in thermosome assemblies containing CCT1:CCT2, followed by assemblies containing CCT1:CCT2:CCT3. Not required for thermosome ATPase activity. Not required for growth. The thermosome or CCT complex is a oligomeric complex of two octameric double-ring structures; the complex is probably a heterooligomer of CCT1, CCT2 AND CCT3 with yet unknown stoichiometry. By heat shock (at protein level). Cannot be stably overexpressed. Belongs to the TCP-1 chaperonin family.