PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. FKBP-13 may play a role in protein trafficking in the ER. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Inhibited by both FK506 and rapamycin. Binds FK506 with 15-fold lower affinity than FKB1. Is not secreted and probably localized in the endoplasmic reticulum. Present with 5400 molecules/cell in log phase SD medium. Belongs to the FKBP-type PPIase family. FKBP2 subfamily.