Regulates the GDP/GTP exchange reaction of most Rab proteins by inhibiting the dissociation of GDP from them, and the subsequent binding of GTP to them.
Brain; predominant in neural and sensory tissues.
Defects in GDI1 are the cause of mental retardation X-linked type 41 (MRX41) [MIM:300104]. Mental retardation is characterized by significantly sub-average general intellectual functioning associated with impairments in adaptative behavior and manifested during the developmental period. Non-syndromic mental retardation patients do not manifest other clinical signs. Defects in GDI1 are the cause of mental retardation X-linked type 48 (MRX48) [MIM:300104]; also known as MRX3.