RasGrf1 and RasGrf2
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The Ras guanine nucleotide releasing factors (RasGrfs) were initially identified as a result of a search for mammalian homolog(s) of the yeast CDC25 Ras activator protein. Whereas other mammalian RasGEFs identified (belonging to the SOS and GRP families) are more widely expressed, the RasGrf1 and RasGrf2 members of the RasGRF family are preferentially, but not exclusively, expressed in the central nervous system. RasGrf1 and RasGrf2 are large proteins composed by multiple modular domains accounting for protein-protein or protein-lipid interactions which are responsible for functional coupling to upstream and downstream signaling and for fine regulation of their intrinsic exchange activity.
Initial studies showed that both RasGrf1 and RasGrf2 are able to activate canonical Ras proteins (H-Ras, N-Ras, or K-Ras) and Rac1, but only RasGrf1 is able to activate members of the R-Ras subfamily (R-Ras, TC21, M-Ras). Furthermore,...