Rho GTPases regulate a number of important cellular functions in eukaryotes, such as organization of the cytoskeleton, stress-induced signal transduction, cell death, cell growth, and differentiation. We have conducted an extensive screening, characterization, and analysis of genes belonging to the Ras superfamily of GTPases in land plants (embryophyta) and found that the Rho family is composed...

Gem is a Ras-related protein whose expression is induced in several cell types upon activation by extracellular stimuli. With the aim of isolating the cellular partners of Gem that mediate its biological activity we performed a yeast two-hybrid screen and identified a novel protein of 970 amino acids, Gmip, that interacts with Gem through its N-terminal half, and presents a cysteine-rich domain...

Heterotrimeric GPCRs (G-protein-coupled receptors) form the largest group of integral membrane receptor proteins and mediate diverse physiological processes. In addition to signalling via heterotrimeric G-proteins, GPCRs can also signal by interacting with various small G-proteins to regulate downstream effector pathways. The small G-protein superfamily is structurally classified into at least ...

Members of the RAS superfamily of small guanosine triphosphatases (GTPases) transition between GDP-bound, inactive and GTP-bound, active states and thereby function as binary switches in the regulation of various cellular activities. Whereas HRAS, NRAS, and KRAS frequently acquire transforming missense mutations in human cancer, little is known of the oncogenic roles of other small GTPases, inc...

The proteins that possess guanine nucleotide exchange factor (GEF) activity, which include about ~800 G protein coupled receptors (GPCRs),1 15 Arf GEFs,2 81 Rho GEFs,3 8 Ras GEFs,4 and others for other families of GTPases,5 catalyze the exchange of GTP for GDP on all regulatory guanine nucleotide binding proteins. Despite their importance as catalysts, relatively few exchange factors (we are aw...

Monomeric GTPases of the Ras superfamily have a very slow intrinsic GTPase activity which is accelerated by specific GTPase-activating proteins. In contrast to Ras- and Rho-specific GTPase-activating proteins (GAPs) that have been studied in great detail, little is known about the functioning of GAPs specific for Ypt/Rab transport GTPases. We have identified two novel Ypt/Rab-GAPs because of th...

BACKGROUND Ras dexamethasone-induced protein (RASD1) is a member of Ras superfamily of small GTPases. RASD1 regulates various signaling pathways involved in iron homeostasis, growth hormone secretion, and circadian rhythm. However, RASD1 function in oocyte remains unknown. METHODS Using immunohistochemistry, immunofluorescence, and quantitative real-time RT-PCR, RASD1 expression in mouse ovar...

Rab proteins constitute the largest branch of the Ras GTPase superfamily. Rabs use the guanine nucleotide-dependent switch mechanism common to the superfamily to regulate each of the four major steps in membrane traffic: vesicle budding, vesicle delivery, vesicle tethering, and fusion of the vesicle membrane with that of the target compartment. These different tasks are carried out by a diverse...

Regulating signal transduction is serious business. If signals are improperly controlled, aberrant proliferation or inappropriate cell death may result. The Ras superfamily of small guanosine triphosphatases (GTPases) and the heterotrimeric G proteins require GTP binding into their active sites for subsequent activation. Hydrolysis of GTP to GDP precedes, and is a requirement for, inactivation....

Rho and rac, two members of the ras-related superfamily of small GTPases, regulate the polymerization of actin to produce stress fibers and lamellipodia, respectively. We report here that cdc42, another member of the rho family, triggers the formation of a third type of actin-based structure found at the cell periphery, filopodia. In addition to stress fibers, rho controls the assembly of focal...