| Modification Notes |
GTPase-activating proteins (GAPs) accelerate the intrinsic rate of GTP hydrolysis of Ras-related proteins, resulting in downregulation of their active form. TBC1D8 (TBC1 domain family member 8), also known as VRP (Vascular Rab-GAP/TBC-containing protein), AD3 or HBLP1, is an 897 amino acid protein that is thought to function as a GTPase-activator for Rab proteins. TBC1D8 contains one GRAM domain and one Rab-GAP TBC domain, the latter of which is a highly conserved 200 amino acid motif that conveys the catalytic activity of GTPase-activating proteins. Similarly, TBC1D8B (TBC1 domain family member 8B), TBC1D9 (TBC1 domain family member 9), also known as TBC1D9A, and TBC1D9B (TBC1 domain family member 9B), are thought to function as GTPase-activators for Rab proteins. TBC1D8, TBC1D8B and TBC1D9B undergo alternative splicing events to produce additional isoforms. |