What is "cyclophilin"

n. (context protein English) Any of a class of proteins that bind to ciclosporin

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.

Cyclophilin A is a cytosolic and highly abundant protein. The protein belongs to a family of isozymes, including cyclophilins B and C, and natural killer cell cyclophilin-related protein. Major isoforms have been found throughout the cell, including the ER, and some are even secreted.