Cyclophilin is a prokaryotic peptidyl-prolyl cis-trans-isomerase (also called Ppiases), or a rotamase which is found in the bacterium Escherichia coli. Cyclophilin is a periplasmic protein which catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. This type of enzyme accelerates the folding of proteins. It is unlike human cyclophilins in the sense that it is not inhibited by the immunosupressant drug cyclosporin A (CSA).
Cyclophilin is a 166 amino acid residue long polypeptide. Its molecular architecture consists of an eight stranded antiparallel beta-sheet barrel bound by alpha-helices. The right-handed alpha-helices are shown here in magenta, whereas the single 310 alpha helix is shown in blue.