Molecular cloning of cDNAs encoding a guanine-nucleotide-releasing factor for Ras p21.
The stimulation of a variety of cell surface receptors promotes the accumulation of the active, GTP-bound form of Ras proteins in cells. This is a critical step in signal transduction because inhibition of Ras activation by anti-Ras antibodies or dominant inhibitory Ras mutants blocks many of the effects of these receptors on cellular function. To reach the active GTP-bound state, Ras proteins must first release bound GDP. This rate-limiting step in GTP binding is thought to be catalysed by a guanine-nucleotide-releasing factor ( GRF). Here we report the cloning of complementary DNAs from a rat brain library that encode a approximately 140K GRF for Ras p21 (p140Ras- GRF). Its carboxy-terminal region is similar to that of CDC25, a GRF for Saccharomyces cerevisiae RAS. This portion of Ras- GRF accelerated the release of GDP from RasH and RasN p21 in vitro, but not from the related RalA, or CDC42Hs GTP-binding proteins. A region in the amino-terminal end of Ras- GRF is similar to both the human breakpoint cluster protein, Bcr, and the dbl oncogene product, a guanine-nucleotide-releasing factor for CDC42Hs. An understanding of Ras- GRF function will enhance our knowledge of the many signal transduction pathways mediated by Ras proteins.[1]References
- Molecular cloning of cDNAs encoding a guanine-nucleotide-releasing factor for Ras p21. Shou, C., Farnsworth, C.L., Neel, B.G., Feig, L.A. Nature (1992) [Pubmed]
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