Solution structure of FK506 bound to FKBP-12.

The complex of the immunosuppressant FK506 bound to FKBP-12 has been studied in solution using 1H and inverse-detected 13C NMR methods. The resonances of bound, 13C-labelled FK506 were assigned and a set of 66 intraligand NOE distance restraints were used to calculate the structure of the bound ligand by distance geometry and restrained molecular dynamics methods. The structure of bound FK506 in solution closely resembles that seen in the X-ray structure [17], except for the allyl region. The differences reflect the influence of intermolecular crystal contacts and have implications for interpretation of the interaction of the FK506/FKBP complex with its putative biological receptor.