FKBP4 (FK506 Binding Protein 4, 59kD, FK506 binding protein 4, FKBP52, FKBP59, HBI, Hsp56, PPIase, p52, HSP binding immunophilin, T-cell FK506-binding protein, peptidylprolyl cis-trans isomerase, rotamase)

Hsp90 is crucial to cellular signaling by its regulation of the folding, activity, and stability of a wide range of client proteins. These client protein complexes may also contain one or more cochaperones (1). One class of Hsp90-binding cochaperone is composed of proteins with a characteristic tetratricopeptide repeat (TPR) domain that forms an Hsp90 binding site. Among the TPR co-chaperones of Hsp90 are Hop/Sti1, protein phosphatase PP5, and members of both the FK506- and cyclosporin A- binding families of immunophilins (2). FK506-binding protein 51 (FKBP51) and FKBP52 are large molecular weight immunophilins that are part of the mature glucocorticoid receptor (GR) heterocomplex (3). The N terminal domain of each protein binds FK506 and has peptidyl-prolyl isomerase (PPIase) activity that converts prolyl peptide bonds within target proteins from cis- to trans- proline. The C-terminal domains contain the TPR repeats involved in protein-protein interactions with the Hsp90 (4). Although FKBP52 and FKBP51 share ~75% sequence similarity, they affect hormone binding by glucocorticoid receptor in opposing manners and have different Hsp90- binding characteristics (3, 5). Also, whereas FKBP51 typically has a role with the progesterone receptor, FKBP52 has been found to be linked to the progesterone, androgen and glucocorticoid receptors (5). Positive Control: Whole tissue extracts from rat kidney and rat and mouse testes. Applications: Suitable for use in Western Blot, Immunoprecipitation and Immunohistochemistry. Other applications not tested. Recommended Dilution: Western Blot:1:2000 Immunohistochemistry:1:250 Immunoprecipitation:1:250 Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4 degrees C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20 degrees C. Aliquots are stable for at least 12 months. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.