The Ras superfamily at a glance

The Ras superfamily of small guanosine triphosphatases (GTPases) comprise over 150 human members (Table S1 in supplementary material), with evolutionarily conserved orthologs found in Drosophila, C. elegans, S. cerevisiae, S. pombe, Dictyostelium and plants (Colicelli, 2004). The Ras oncogene proteins are the founding members of this family, which is divided into five major branches on the basis of sequence (Fig. S1 in supplementary material) and functional similarities: Ras, Rho, Rab, Ran and Arf. Small GTPases share a common biochemical mechanism and act as binary molecular switches (Vetter and Wittinghofer, 2001). Although similar to the heterotrimeric G protein α subunits in biochemistry and function, Ras…