page_title: Cyclophilin
section_title: Cyclophilin A
hierarchical_section_title: Cyclophilin / Mammalian cyclophilins / Cyclophilin A
caption_attribution_description: English: Cyclophilin A + HIV peptid (green), Human
context_page_description: Cyclophilins are a family of proteins named after their ability to bind to ciclosporin, an immunosuppressant which is usually used to suppress rejection after internal organ transplants. They are found in all domains of life. 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 within single cells, including inside the Endoplasmic reticulum, and some are even secreted.
context_section_description: Cyclophilin A (CYPA) also known as peptidylprolyl isomerase A (PPIA), which is found in the cytosol, has a beta barrel structure with two alpha helices and a beta-sheet. Other cyclophilins have similar structures to cyclophilin A. The cyclosporin-cyclophilin A complex inhibits a calcium/calmodulin-dependent phosphatase, calcineurin, the inhibition of which is thought to suppress organ rejection by halting the production of the pro-inflammatory molecules TNF alpha and interleukin 2.
  Cyclophilin A is also known to be recruited by the Gag polyprotein during HIV-1 virus infection, and its incorporation into new virus particles is essential for HIV-1 infectivity.
caption: Cyclophilin A + HIV peptid (green), Human.
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