Signal transduction via Ras.

Ras is a major regulator of cell growth. It is a GTP-binding protein that functions as a molecular switch, cycling between the GDP-bound OFF and GTP-bound ON states. In the GTP-bound state it interacts with effector proteins that mediate the biological function. It is found as an oncogene in about 30% of human tumors. Structural and mechanistic studies on Ras and its interaction with effectors and GAP will be discussed in the context of the biology and pathophysiology of this protein.