Recent advances in molecular biology have shown GTPases and phosphoproteins to be the paramount molecular switches utilized intracellularly in biological systems. The origins of the GTPase switch appear to be almost as ancient as life itself, and through evolution nature has adapted this switch to a variety of purposes. In this two-volume work a broad survey of the major classes of GTPases is presented. The role of GTPases in ensuring accuracy during protein translation, a new look at the trimeric G-protein cycle, the molecular function of ARF in vesicle coating, the emerging role of the...