Figure 2. Summary of CPN20 functions. (A) CPN20 functions as a co-chaperonin, which assists the chaperonin CPN60 in folding the denatured proteins in an ATP-dependent way. (B) We demonstrate the additional function of CPN20 in FeSOD activation. We propose two possible models for the mechanism: Model 1, CPN20 transfers its bound Fe to FeSOD, thus activating FeSOD; Model 2, CPN20 might help in conformational changes or modifications of the FeSOD for the co-factor Fe to be incorporated into the reaction site properly.