FKBP4 act as a regulator of microtubule dynamics by inhibiting MAPT/TAU ability to promote microtubule assembly. FKBP4 may play a role in the intracellular trafficking of heterooligomeric forms of steroid hormone receptors between cytoplasm and nuclear compartments, it also may have a protective role against oxidative stress in mitochondria. The isomerase activity controls neuronal growth cones via regulation of TRPC1 channel opening.

FKBP25 contains 1 PPIase FKBP-type domain, belongs to the FKBP-type PPIase family. FK506- and rapamycin-binding proteins (FKBPs) constitute a family of receptors for the two immunosuppressants which inhibit T-cell proliferation by arresting two distinct cytoplasmic signal transmission pathways. FKBP3 is a cis-trans prolyl isomerase enzyme that binds the immunosuppressants FK506 and rapamycin, as well as histone deacetylases, the transcription factor YY1, casein kinase II, and nucleolin. It has a higher affinity for rapamycin than for FK506 and thus may be an important target molecule for immunosuppression by rapamycin.

Peptidyl-prolyl cis-trans isomerase FKBP2(FKBP2 for short), also named 13 kDa FK506-binding protein, FK506-binding protein 2, Immunophilin FKBP13, Rotamase, is a endoplasmic reticulum peripheral membrane protein. It contains 1 PPIase FKBP-type domain and belongs to the FKBP-type PPIase family, FKBP2 subfamily which takes part in immunoregulation and basic cellular processes involving protein folding and trafficking. FKBP2 is a cis-trans prolyl isomerase that binds the immunosuppressants FK506 and rapamycin. FKBP2 functions as an ER chaperone and as a component of membrane cytoskeletal scaffolds.