 GEF binding induces conformational changes in the P loop and switch regions of the GTPase while the rest of the structure is largely unchanged.The binding of the GEF sterically hinders the magnesium-binding site and interferes with the phosphate-binding region, while the base-binding region remains accessible.When the GEF binds the GTPase, the phosphate groups are released first and the GEF is displaced upon binding of the entering GTP molecule.