GDIs sequester the inactive GTPases, preventing the dissociation of GDP and interactions with regulatory and effector molecules. They maintain Rho GTPases as soluble cytosolic proteins by forming high affinity complexes. In these complexes, the geranylgeranyl membrane targeting moiety present at the C terminus of the Rho GTPases is shielded from the solvent by its insertion into the hydrophobic pocket formed by the immunoglobulin like beta sandwich of the GDI (DerMardirossian and Bokoch, 2005).
Rho proteins, when released from the sequestering cytosolic GDIs, insert into the lipid bilayer of the plasma membrane with their isoprenylated C termini. The membrane bound GEFs activate these free RhoGTPases and thereby trigger the downstream signaling events via respective effector proteins on the membrane (Robbe et al., 2003).