PPIase independent chaperone‐like function of recombinant human Cyclophilin A during arginine kinase refolding

Whether Cyclophilin A (CyPA) functions as a foldase or a chaperone when assisting protein folding has long been argued. In this study, we engineered four variants of recombinant human Cyclophilin A (rhCyPA), all of which were inactive to tetrapeptide substrate Suc-AAPF-pNA. However, these variants were able to suppress aggregation during arginine kinase (AK) refolding as efficient as wild-type rhCyPA, especially, variant Q63A had even more efficiency to suppress aggregation and improve reactivation yields of AK. These results indicate that rhCyPA have peptidyl-prolyl cis-trans isomerase (PPIase) independent chaperone-like activity during AK folding. In addition, results suggest that surface hydrophobicity of rhCyPA can suppress AK aggregation and binding to rhCyPA hydrophobic active pocket is a prerequisite for chaperoning AK folding.