Design, synthesis, and kinetic evaluation of high-affinity FKBP ligands and the X-ray crystal structures of their complexes with FKBP12

The design and synthesis of high-affinity FKBP12 ligands is described. These compounds potently inhibit the cis-trans-peptidylprolyl isomerase (rotamase) activity catalyzed by FKBP12 with inhibition constants (K sub(i,app)) as low as 1 nM, yet they possess remarkable structural simplicity relative to FK506 and rapamycin, from which they are conceptually derived. The atomic structures of three FKBP12-ligand complexes and of one unbound ligand were determined by X-ray crystallography and are compared to the FKBP12-FK506 and FKBP12-rapamycin complexes.