Conformational dynamics of a regulator of G-protein signaling protein reveals a mechanism of allosteric inhibition by a small molecule.

Academic Article


  • Regulators of G protein signaling (RGS) proteins are key players in regulating signaling via G protein-coupled receptors. RGS proteins directly bind to the Gα-subunits of activated heterotrimeric G-proteins, and accelerate the rate of GTP hydrolysis, thereby rapidly deactivating G-proteins. Using atomistic simulations and NMR spectroscopy, we have studied in molecular detail the mechanism of action of CCG-50014, a potent small molecule inhibitor of RGS4 that covalently binds to cysteine residues on RGS4. We apply temperature-accelerated molecular dynamics (TAMD) to carry out enhanced conformational sampling of apo RGS4 structures, and consistently find that the α5-α6 helix pair of RGS4 can spontaneously span open-like conformations, allowing binding of CCG-50014 to the buried side-chain of Cys95. Both NMR experiments and MD simulations reveal chemical shift perturbations in residues in the vicinity of inhibitor binding site as well as in the RGS4-Gα binding interface. Consistent with a loss of G-protein binding, GAP activity, and allosteric mechanism of action of CCG-50014, our simulations of the RGS4-Gα complex in the presence of inhibitor suggest a relatively unstable protein-protein interaction. These results have potential implications for understanding how the conformational dynamics among RGS proteins may play a key role in the sensitivity of inhibitors.
  • Authors

  • Vashisth, Harish
  • Storaska, Andrew J
  • Neubig, Richard R
  • Brooks, Charles L
  • Status

    Publication Date

  • December 20, 2013
  • Published In


  • Allosteric Regulation
  • Allosteric Site
  • Cysteine
  • Humans
  • Kinetics
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • RGS Proteins
  • Small Molecule Libraries
  • Thiazolidinediones
  • Digital Object Identifier (doi)

    Start Page

  • 2778
  • End Page

  • 2784
  • Volume

  • 8
  • Issue

  • 12