GEM - AN INDUCED, IMMEDIATE-EARLY PROTEIN BELONGING TO THE RAS FAMILY

A gene encoding a 35-kilodalton guanosine triphosphate (GTP)-binding p rotein, Gem, was cloned from mitogen-induced human peripheral blood T cells. Gem and Rad, the product of a gene overexpressed in skeletal mu scle in individuals with Type II diabetes, constitute a new family of Ras-related GTP-binding proteins. The distinct structural features of this family include the G3 GTP-binding motif, extensive amino- and car boxyl-terminal extensions beyond the Ras-related domain, and a motif t hat determines membrane association. Gem was transiently expressed in human peripheral blood T cells in response to mitogenic stimulation; t he protein was phosphorylated on tyrosine residues and localized to th e cytosolic face of the plasma membrane. Deregulated Gem expression pr evented proliferation of normal and transformed 3T3 cells. These resul ts suggest that Gem is a regulatory protein, possibly participating in receptor-mediated signal transduction at the plasma membrane.