RasGrf (RAS Protein-Specific Guanine Nucleotide-Releasing Factor)
The Ras guanine nucleotide releasing factor (RasGrf) proteins were isolated in an effort to find mammalian homolog(s) of the yeast CDC25 Ras activator protein. The search for mammalian Ras GEFs during the early 1990s led to the discovery and isolation of the Son of sevenless (Sos) and the RasGrf proteins. Whereas the Sos proteins had ubiquitous expression, RasGrf expression was restricted mainly to the central nervous system. Soon after the discovery of the first member of the RasGrf family (RasGrf1) in neural tissues, a second highly homologous member of this family was isolated from embryonic stem cells (RasGrf2). Later on, a number of distinct, alternatively spliced isoforms have been described for both genes in a variety of tissues or developmental stages. RasGrf1 and RasGrf2 are large, modular proteins composed by multiple functional domains accounting for protein–protein or protein–lipid interactions which are...