GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a protein domain common to many GTPases.
The Rab family of proteins is a member of the Ras superfamily of small G proteins. Approximately 70 types of Rabs have now been identified in humans. Rab proteins generally possess a GTPase fold, which consists of a six-stranded beta sheet which is flanked by five alpha helices. Rab GTPases regulate many steps of membrane trafficking, including vesicle formation, vesicle movement along actin and tubulin networks, and membrane fusion. These processes make up the route through which cell surface proteins are trafficked from the Golgi to the plasma membrane and are recycled. Surface protein recycling returns proteins to the surface whose function involves carrying another protein or substance inside the cell, such as the transferrin receptor, or serves as a means of regulating the number of a certain type of protein molecules on the surface.
In molecular biology, the Guanosine dissociation inhibitors (GDIs) constitute a family of small GTPases that serve a regulatory role in vesicular membrane traffic. GDIs bind to the GDP-bound form of Rho and Rab small GTPases and not only prevent exchange, but also prevent the small GTPase from localizing at the membrane, which is their place of action. This inhibition can be removed by the action of a GDI displacement factor. GDIs also inhibit cdc42 by binding to its tail and preventing its insertion into membranes; hence it cannot trigger WASPs and cannot lead to nucleation of F-actin.
Transforming protein RhoA, also known as Ras homolog family member A (RhoA), is a small GTPase protein in the Rho family of GTPases that in humans is encoded by the RHOA gene. While the effects of RhoA activity are not all well known, it is primarily associated with cytoskeleton regulation, mostly actin stress fibers formation and actomyosin contractility. It acts upon several effectors. Among them, ROCK1 and DIAPH1 are the best described. RhoA, and the other Rho GTPases, are part of a larger family of related proteins known as the Ras superfamily, a family of proteins involved in the regulation and timing of cell division. RhoA is one of the oldest Rho GTPases, with homologues present in the genomes since 1.5 billion years. As a consequence, RhoA is somehow involved in many cellular processes which emerged throughout evolution. RhoA specifically is regarded as a prominent regulatory factor in other functions such as the regulation of cytoskeletal dynamics, transcription, cell cycle progression and cell transformation.
Rab GDP dissociation inhibitor alpha is a protein that in humans is encoded by the GDI1 gene.
Rac2 is a small signaling G protein, and is a member of the Rac subfamily of the family Rho family of GTPases. It is encoded by the gene RAC2.
cAMP-dependent protein kinase catalytic subunit beta is an enzyme that in humans is encoded by the PRKACB gene.
Rho GDP-dissociation inhibitor 1 is a protein that in humans is encoded by the ARHGDIA gene.
Calcium/calmodulin-dependent protein kinase type II delta chain is an enzyme that in humans is encoded by the CAMK2D gene.
Eukaryotic translation initiation factor 2 subunit 2 (eIF2β) is a protein that in humans is encoded by the EIF2S2 gene.
Ras-related protein Rab-8A is a protein that in humans is encoded by the RAB8A gene.
Rho GDP-dissociation inhibitor 2 is a protein that in humans is encoded by the ARHGDIB gene. Aliases of this gene include RhoGDI2, GDID4, Rho GDI 2, and others.
Interferon-induced guanylate-binding protein 1 is a protein that in humans is encoded by the GBP1 gene. It belongs to the dynamin superfamily of large GTPases.
Ras-related protein Rab-9A is a protein that in humans is encoded by the RAB9A gene.
Protein tyrosine phosphatase type IVA 2 is an enzyme that in humans is encoded by the PTP4A2 gene.
Ras-related protein Rab-3D is a protein that in humans is encoded by the RAB3D gene.
Rho GDP-dissociation inhibitor 3 is a protein that in humans is encoded by the ARHGDIG gene.
Ras-related protein Rab-25 is a protein that in humans is encoded by the RAB25 gene. It is thought to act as a promoter of tumor development.
Rap1 GTPase-GDP dissociation stimulator 1 is an enzyme that in humans is encoded by the RAP1GDS1 gene.
Ras-related protein Rab-2B is a protein that in humans is encoded by the RAB2B gene.
