A protein (GTP dissociation inhibitor) that inhibits GDP/GTP exchange on ras-like GTPases so that they remain in the active GTP-bound form. Different families of GTPases have specific GDIs (e.g. rho-GDI). Mutations in the rab-GDI (GDI-1, oligophrenin, see p21 activated kinases) are associated with some types of X-linked mental retardation. GDI-D4 is the rho-GDIb. The GDI displacement factor (GDF) is a membrane-associated protein (~25 kDa) that is involved in the dissociation of GDI from prenylated rab following membrane binding.
Subjects: Medicine and Health.