Crystal structure of a Protein Phosphatase-1: Calcineurin Hybrid Bound to Okadaic Acid

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.218 

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Crystal Structure and Mutagenesis of a Protein Phosphatase-1:Calcineurin Hybrid Elucidate the Role of the {beta}12-{beta}13 Loop in Inhibitor Binding

Maynes, J.T.Perreault, K.R.Cherney, M.M.Luu, H.A.James, M.N.G.Holmes, C.F.B.

(2004) J Biol Chem 279: 43198-43206

  • DOI: https://doi.org/10.1074/jbc.M407184200
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Protein phosphatase-1 and protein phosphatase-2B (calcineurin) are eukaryotic serine/threonine phosphatases that share 40% sequence identity in their catalytic subunits. Despite the similarities in sequence, these phosphatases are widely divergent when it comes to inhibition by natural product toxins, such as microcystin-LR and okadaic acid. The most prominent region of non-conserved sequence between these phosphatases corresponds to the beta12-beta13 loop of protein phosphatase-1, and the L7 loop of toxin-resistant calcineurin. In the present study, mutagenesis of residues 273-277 of the beta12-beta13 loop of the protein phosphatase-1 catalytic subunit (PP-1c) to the corresponding residues in calcineurin (312-316), resulted in a chimeric mutant that showed a decrease in sensitivity to microcystin-LR, okadaic acid, and the endogenous PP-1c inhibitor protein inhibitor-2. A crystal structure of the chimeric mutant in complex with okadaic acid was determined to 2.0-A resolution. The beta12-beta13 loop region of the mutant superimposes closely with that of wild-type PP-1c bound to okadaic acid. Systematic mutation of each residue in the beta12-beta13 loop of PP-1c showed that a single amino acid change (C273L) was the most influential in mediating sensitivity of PP-1c to toxins. Taken together, these data indicate that it is an individual amino acid residue substitution and not a change in the overall beta12-beta13 loop conformation of protein phosphatase-1 that contributes to disrupting important interactions with inhibitors such as microcystin-LR and okadaic acid.

  • Organizational Affiliation

    Canadian Institutes of Health Research, Group in Protein Structure and Function, Department of Biochemistry, Faculty of Medicine, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Serine/threonine protein phosphatase PP1-gamma catalytic subunit293Homo sapiensMutation(s): 5 
Gene Names: PPP1CC
UniProt & NIH Common Fund Data Resources
Find proteins for P36873 (Homo sapiens)
Explore P36873 
Go to UniProtKB:  P36873
GTEx:  ENSG00000186298 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP36873
Sequence Annotations
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
OKA BindingDB:  1U32 IC50: min: 20, max: 5000 (nM) from 8 assay(s)
PDBBind:  1U32 IC50: 97 (nM) from 1 assay(s)
Binding MOAD:  1U32 IC50: 97 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.218 
  • Space Group: P 42 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 98.759α = 90
b = 98.759β = 90
c = 62.18γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-08-17
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2021-11-10
    Changes: Database references, Derived calculations
  • Version 1.4: 2023-10-25
    Changes: Data collection, Refinement description