Phospho-pivot modeling predicts specific interactions of protein phosphatase-1 with a phospho-inhibitor protein CPI-17

J Biochem. 2005 May;137(5):633-41. doi: 10.1093/jb/mvi077.


Phospho-amino acids in proteins are directly associated with phospho-receptor proteins, including protein phosphatases. Here we produced and tested a scheme for docking together interacting phospho-proteins whose monomeric 3D structures were known. The phosphate of calyculin A, an inhibitor for protein phosphatase-1 and 2A (PP1 and PP2A), or phospho-CPI-17, a PP1-specific inhibitor protein, was docked at the active site of PP1. First, a library of 186,624 virtual complexes was generated in silico, by pivoting the phospho-ligand at the phosphorus atom by step every 5 degrees on three rotational axes. These models were then graded for probability according to atomic proximity between two molecules. The predicted structure of PP1 x calyculin A complex fitted to the crystal structure with r.m.s.d. of 0.23 A, providing a validate test of the modeling method. Modeling of PP1 x phospho-CPI-17 complex yielded one converged structure. The segment of CPI-17 around phospho-Thr38 is predicted to fit in the active site of PP1. Positive charges at Arg33/36 of CPI-17 are in close proximity to Glu274 of PP1, where the sequence is unique among Ser/Thr phosphatases. Single mutations of these residues in PP1 reduced the affinity against phospho-CPI-17. Thus, the interface of the PP1 x CPI-17 complex predicted by the phospho-pivot modeling accounts for the specificity of CPI-17 against PP1.

MeSH terms

  • Animals
  • Binding Sites
  • Computer Simulation
  • Marine Toxins
  • Models, Molecular
  • Oxazoles / pharmacology
  • Phosphoprotein Phosphatases / antagonists & inhibitors*
  • Phosphoprotein Phosphatases / metabolism*
  • Phosphoproteins / chemistry
  • Phosphoproteins / metabolism*
  • Phosphoproteins / pharmacology
  • Protein Phosphatase 1
  • Rabbits
  • Thermodynamics


  • Marine Toxins
  • Oxazoles
  • Phosphoproteins
  • calyculin A
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 1