Cyclophilin B: Proteins and Enzymes

Cyclophilin B (SCYLP, CyPB and peptidyl-prolyl cis-trans isomerase B) is a 24 kDa glycoprotein member of the B subfamily of the cyclophilin-type PPIase family of molecules. It is both secreted and retained in the ER. When secreted, Cyclophilin B mediates chemotaxis and T cell adhesion to fibronectin. This is likely due to its prolyl cis/trans isomerase activity. Intracellularly, Cyclophilin B appears to serve as a molecular chaperone for molecules destined for secretion. It does so via stabilization, and facilitating the activity of additional chaperones. The human Cyclophilin B precursor is 216 amino acids (aa) in length. It contains a 25 aa signal sequence plus a 191 aa mature region. There is a partial heparin-binding sequence (aa 27-34), a PPIase domain (aa 47-204) and a C-terminal ER retention motif (aa 213-216). Over aa 34-216, the human and mouse sequences are 95% aa identical.