FKBP2 is also named as FKBP13 and belongs to the FKBP-type PPIase family. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. FKBP2 has a 21-amino acid signal peptide and appears to be membrane-associated. It is localized to the lumen of the endoplasmic reticulum (ER). FKBP12 and FKBP13 are highly similar proteins,of molecular masses 12 kDa and 13 kDa respectively,with approx.43 % amino acid identity. The strong homology between FKBP12 and FKBP13 suggests that they may share similar biological functions,although,apart from rotamase activity,details relating to the function of either protein are scant.