Ras-related proteins

Rab proteins A family of ras-related proteins first observed in rat brain they are GTPases and are active when GTP is found... 

Rab is a family of small G proteins involved in membrane vesicle trafficking. Mammalian tissues contain around 30 forms of Rab, which specifically associate with the various types of membrane vesicles and organelles that exist in cells [30,31]. Rab proteins, named originally as ras-related proteins in brain, are isoprenylated and associate with membranes, as do isoprenylated Ras and G protein y subunits. However, unlike these other G proteins, the GTP and GDP binding to Rab appears to regulate its association with membrane compartments. 

There are several possible explanations to account for this apparent lack of toxicity. Some geranylgeranylated Ras-related proteins might compensate for the loss of Ras function (see, e.g., [46]). Alternatively inhibition of farnesyl transferase may reduce Ras activity below the level required for transformation, yet allow sufficient Ras activity for maintaining normal cell viability [47]. Alternatively, a different signaling pathway may be activated when Ras is not anchored to the plasma membrane. 

Surprisingly, AGS 1 is a Ras-related protein with all the conserved Ras-like motifs required for nucleotide binding/hydrolysis and membrane localization (Fig. 4). AGSl also contains unique N- and C-terminal extensions not seen in the majority of Ras family members, as well as a short internal insert region (Fig. 4). Each of these extensions in AGS 1 con-... 

Cismowski MJ, Ma C, Ribas C, Xie X, Spruyt M, Lizano JS, Lanier SM, Duzic E (2000) Activation of heterotrimeric G-protein signaling by a ras-related protein implications for signal integration. J Biol Chem 275 23421-23424... 

The lifetime of the active GTP-bound state may be reduced by regulatory GTPase activating proteins. The primary fimction of the GTPase activating proteins (GAP) is to negatively regulate the Ras proteins and Ras-related proteins. 

The GAP proteins stimulate GTPase activity of the corresponding Ras protein by an active role in catalysis. This mechanism of GTPase stimulation by GAP protein has largely been explained, thanks to the crystal structure of the Ras GAP transition state analog complex (see 9.2.2). The crystal structure of the transition state complex of a Ras-related protein, the RhoA protein, with the corresponding GAP protein has also shown a similar mechanism of GTPase stimulation. 

Ras-related protein 11A P62491 (h) RAB11A RAB11A (h) 15q21.3-q22.31 (h) 216 (h)... 

Ras-related protein 11A (RAB 11 A) Human (None) (None) (None)... 

Lapetina, E.G., Lacal, J.C., Reep, B.R., and Molina y Vedia, L. (1989). A ras-related protein is phosphorylated and translocated by agonists that increase cAMP levels in hnman platelets. Proc Natl Acad Sci USA 86 3131-3134. 

Takahashi, K., Nakagawa, M., Young, S.G., and Yamanaka, S. (2005). Differential membrane localization of ERas and Rheb, two Ras-related proteins involved in the phosphatidylinositol 3-kinase/mTOR pathway. J Biol Chem 280 32768-32774. 

Philips, M.R., et al. (1993). Carboxyl methylation of Ras-related proteins during signal transduction in neutrophils. Science 259 977-980. 

Holstein, S.A., Wohlford-Lenane, C.L., and Hohl, R.J. (2002). Isoprenoids influence expression of Ras and Ras-related proteins. Biochemistry 41 13698-13704. 

Ras membrane association. For example, treatment of cells that express GFP-H-Ras with FTTs causes GFP-H-Ras to mislo-calize to the cytoplasm, which indicates that famesylation is required for membrane association. Compounds that block protein palmitoylation, such as 2-bromopalmitate, can also be used to determine whether palmitoylation is required for Ras-related proteins to associate with the plasma membrane (46 8). 

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