sentences:  RAS genes (e.g., MIM 190020) encode membrane-bound guanine nucleotide-binding proteins that function in the transduction of signals that control cell growth and differentiation.Binding of GTP activates RAS proteins, and subsequent hydrolysis of the bound GTP to GDP and phosphate inactivates signaling by these proteins.GTP binding can be catalyzed by guanine nucleotide exchange factors for RAS, and GTP hydrolysis can be accelerated by GTPase-activating proteins (GAPs).