The Ras binding domain (RBD) of the c-Raf kinase protein (Raf) protein has been expressed as a GST-fusion protein in E. coli. This protein binds binds specifically to GTP-bound, and not GDP-bound, Ras proteins. The domain can therefore be used to specifically precipitate active, GTP-bound Ras as well as to specifically block the activity of Ras in vitro and in vivo.nnThe protein is supplied in a glutathione agarose bound format and is shipped lyophilized. The beads are colored for ease of use. This product is used in our Ras activation assay Biochem Kit™ (Cat. # BK008). The GST-tagged Raf-RBD protein can be released from the beads by incubation with 10 mM reduced glutathione.