How RhoGDI binds Rho

Acta Crystallogr D Biol Crystallogr. 1999 Sep;55(Pt 9):1503-15. doi: 10.1107/s090744499900801x.


Like all Rho (Ras homology) GTPases, RhoA functions as a molecular switch in cell signaling, alternating between GTP- and GDP-bound states, with its biologically inactive GDP-bound form maintained as a cytosolic complex with RhoGDI (guanine nucleotide-exchange inhibitor). The crystal structures of RhoA-GDP and of the C-terminal immunoglobulin-like domain of RhoGDI (residues 67-203) are known, but the mechanism by which the two proteins interact is not known. The functional human RhoA-RhoGDI complex has been expressed in yeast and crystallized (P6(5)22, unit-cell parameters a = b = 139, c = 253 A, two complexes in the asymmetric unit). Although diffraction from these crystals extends to 3.5 A and is highly anisotropic, the experimentally phased (MAD plus MIR) electron-density map was adequate to reveal the mutual disposition of the two molecules. The result was validated by molecular-replacement calculations when data were corrected for anisotropy. Furthermore, the N-terminus of RhoGDI (the region involved in inhibition of nucleotide exchange) can be identified in the electron-density map: it is bound to the switch I and switch II regions of RhoA, occluding an epitope which binds Dbl-like nucleotide-exchange factors. The entrance of the hydrophobic pocket of RhoGDI is 25 A from the last residue in the RhoA model, with its C-terminus oriented to accommodate the geranylgeranyl group without conformational change in RhoA.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Crystallography, X-Ray
  • Cytosol / metabolism
  • Dimerization
  • GTP Phosphohydrolases / metabolism
  • GTP-Binding Proteins / biosynthesis
  • GTP-Binding Proteins / chemistry
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Guanine Nucleotide Dissociation Inhibitors*
  • Humans
  • Oligopeptides / metabolism
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Reproducibility of Results
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • rho Guanine Nucleotide Dissociation Inhibitor alpha
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors
  • rhoA GTP-Binding Protein


  • ARHGDIA protein, human
  • Guanine Nucleotide Dissociation Inhibitors
  • Oligopeptides
  • rho Guanine Nucleotide Dissociation Inhibitor alpha
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • rhoA GTP-Binding Protein

Associated data

  • PDB/1CC0