title: The Ras-related protein R-ras interacts directly with Raf-1 in a GTP-dependent manner.
abstract: R-ras is a member of the ras family of small GTPases that associates with the apoptosis-suppressing proto-oncogene product Bcl-2. Using the yeast two-hybrid system we provide evidence for an interaction between R-ras and the Raf-1 kinase. This interaction requires only the N-terminal regulatory domain (amino acids 1-256) of Raf-1, and is observed with both the wild type and a constitutively active R-ras mutant, but not with a deletion mutant that lacks the potential effector domain or a mutant of R-ras impaired for GTP binding. Moreover, using an in vitro binding assay we show a direct GTP-dependent interaction of purified R-ras with a purified Raf-1 fragment corresponding to the proposed 81-amino-acid H-Ras-binding domain of Raf-1 (amino acids 51-131). Taken together, these data indicate that R-ras may exert its biological effect by means of modulating the activity of the Raf-1 kinase as its direct downstream effector.
authors.affiliation: ONYX Pharmaceuticals, Richmond, CA 94806.
authors.forename: M
authors.initials: M
authors.lastname: Spaargaren
authors.forename: G A
authors.initials: GA
authors.lastname: Martin
authors.forename: F
authors.initials: F
authors.lastname: McCormick
authors.forename: M J
authors.initials: MJ
authors.lastname: Fernandez-Sarabia
authors.forename: J R
authors.initials: JR
authors.lastname: Bischoff
mesh_terms: D000818:Animals; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D017384:Sequence Deletion; D018631:ras Proteins
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D006160:Guanosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C085929:RRAS protein, human; D018631:ras Proteins