Peptidyl-prolyl cis-trans isomerase A is a cytoplasm protein which belongs to the cyclophilin-type PPIase family and PPIase A subfamily. Cyclophilins(CyPs) are a family of proteins found in organisms ranging from prokaryotes to humans. These molecules exhibit peptidyl-prolyl isomerase activity, suggesting that they influence the conformation of proteins in cells. Cyclophilin A accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Cyclophilin A can interact with several HIV proteins, including p55 gag, Vpr, and capsid protein, and has been shown to be necessary for the formation of infectious HIV virions.