FK506 binding protein 1A, 12kDa Adenovirus (Ad-FKBP12)

The immunophilins are a highly conserved family of cis-trans peptidyl-prolyl isomerases that bind to and mediate the effects of immunosuppressive drugs, such as cyclosporin, FK506 and rapamycin. Several related immunophilins, FKBP12, FKBP51 and FKBP52 are characterized as cytosolic FK506-binding proteins. Following ligand binding, they functionally inhibit the phosphatase activity of calcineurin. These related proteins have distinct molecular masses and differential expression patterns. FKBP12 and FKBP52 are both widely expressed and have molecular masses of 12 kDa and 52 kDa, respectively. FKBP51 is a 51 kDa protein that is predominantly expressed in T cells, where it blocks T cell activation.