Crystal structures of human calcineurin and the human FKBP12-FK506-calcineurin complex.
Kissinger CR,
Parge HE,
Knighton DR,
Lewis CT,
Pelletier LA,
Tempczyk A,
Kalish VJ,
Tucker KD,
Showalter RE,
Moomaw EW, et al.
Agouron Pharmaceuticals Inc., San Diego, California 92121-1121, USA.
Calcineurin (CaN) is a calcium- and calmodulin-dependent protein serine/threonine phosphate which is critical for several important cellular processes, including T-cell activation. CaN is the target of the immunosuppressive drugs cyclosporin A and FK506, which inhibit CaN after forming complexes with cytoplasmic binding proteins (cyclophilin and FKBP12, respectively). We report here the crystal structures of full-length human CaN at 2.1 A resolution and of the complex of human CaN with FKBP12-FK506 at 3.5 A resolution. In the native CaN structure, an auto-inhibitory element binds at the Zn/Fe-containing active site. The metal-site geometry and active-site water structure suggest a catalytic mechanism involving nucleophilic attack on the substrate phosphate by a metal-activated water molecule. In the FKBP12-FK506-CaN complex, the auto-inhibitory element is displaced from the active site. The site of binding of FKBP12-FK506 appears to be shared by other non-competitive inhibitors of calcineurin, including a natural anchoring protein.
PMID: 8524402 [PubMed - indexed for MEDLINE]