Abstract
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.
MeSH terms
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A Kinase Anchor Proteins
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Adaptor Proteins, Signal Transducing*
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Amino Acid Sequence
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Binding Sites
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Calcineurin
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Calcium / metabolism
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Calmodulin-Binding Proteins / antagonists & inhibitors
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Calmodulin-Binding Proteins / chemistry*
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Calmodulin-Binding Proteins / metabolism
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Calmodulin-Binding Proteins / ultrastructure
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Carrier Proteins / chemistry
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Carrier Proteins / metabolism*
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Crystallization
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Crystallography, X-Ray
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / metabolism*
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Enzyme Inhibitors / metabolism
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Enzyme Inhibitors / pharmacology
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Heat-Shock Proteins / chemistry
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Heat-Shock Proteins / metabolism*
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Humans
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Hydrogen Bonding
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Models, Molecular
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Molecular Sequence Data
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Phosphoprotein Phosphatases / antagonists & inhibitors
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Phosphoprotein Phosphatases / chemistry*
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Phosphoprotein Phosphatases / metabolism
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Phosphoprotein Phosphatases / ultrastructure
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Protein Conformation
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Protein Structure, Secondary
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Proteins / metabolism
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Proteins / pharmacology
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Recombinant Proteins / chemistry
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Tacrolimus / chemistry
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Tacrolimus / metabolism*
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Tacrolimus Binding Proteins
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Water / metabolism
Substances
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A Kinase Anchor Proteins
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AKAP5 protein, human
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Adaptor Proteins, Signal Transducing
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Calmodulin-Binding Proteins
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Carrier Proteins
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DNA-Binding Proteins
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Enzyme Inhibitors
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Heat-Shock Proteins
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Proteins
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Recombinant Proteins
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Water
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Calcineurin
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Phosphoprotein Phosphatases
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Tacrolimus Binding Proteins
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Calcium
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Tacrolimus