Ral B

RalB is a member of the Ras-like GTP binding protein family. Ras proteins provide a crucial link in the intracellular signalling cascades. Ras proteins are members of the small G protein family. These proteins are characterized by a molecular weight between 20 and 30 kDa, the ability to bind GTP or GDP and a low intrinsic GTPase activity. These proteins relay signals from the plasma membrane activated by receptor tyrosine kinases to the nucleus via a network of serine/threonine kinases. Ras proteins belong to a family of approximately 40 mammalian and 60 non-mammalian proteins. Ras proteins were first discovered as the hyperactive products of mutant Ras genes which promote cancer by disrupting the normal controls on cell proliferation and differentiation; about 30% of human cancers have mutations in a Ras gene. Ras and Ras-like proteins function as switches, cycling between 2 distinct conformational states, active when GTP is bound and inactive when GDP is bound. Affinity precipitation assays can be used to determine the activation status of Ras and Ras-like family members. This assay is based on the ability of the Ras family effector proteins to interact specifically with the activated GTP-bound form of their target GTPases.