Ras is a membrane-associated small G protein that is indirectly coupled to receptor and nonreceptor tyrosine kinases. Ras activation is regulated by the levels of bound GTP and GDP. Several effectors of Ras have been identified, including Raf1, PI 3-kinase and RIN1. RIN1 (Ras interaction/interference) was identified as a Ras-interacting protein in yeast, and it has been shown to bind to the human H-Ras. This RIN1-Ras interaction is enhanced when Ras is bound to GTP. Unlike Raf1, RIN1 is localized primarily to the plasma membrane. RIN1 contains an SH2 domain and an amino-terminal region similar to consensus SH3 domains. RIN1 binds c-Abl and, like Raf1, interacts with 14-3-3 proteins.