Cyclophilin

Cyclophilins are a family of proteins from vertebrates and other organisms that bind to ciclosporin (cyclosporin A), an immunosuppressant which is usually used to suppress rejection after internal organ transplants. These proteins have peptidyl prolyl isomerase activity, which catalyzes the isomerization of peptide bonds from trans form to cis form at proline residues and facilitates protein folding.