The Ras superfamily at a glance

Abstract

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 family proteins function as monomeric G proteins. Variations in structure (Biou and Cherfils, 2004), post-translational modifications that dictate specific subcellular locations and the proteins that serve as their regulators and effectors allow these small GTPases to function as sophisticated modulators of a remarkably complex and diverse range of cellular processes. Here, we present the basic structural features of Ras proteins, with respect to specific Ras sequences, to highlight the general properties of this family of proteins and discuss features that distinguishes the various branches of the superfamily from Ras.FIG1Ras superfamily GTPases function as GDP/GTP-regulated molecular switches (Vetter and Wittinghofer, 2001). They share a set of conserved G box GDP/GTP-…