GTPases are molecular switches that are used to control biochemical pathways. This book describes the properties and cellular roles of all the major families of GTPases: the G proteins, Ras, Rho, Rab, Arf, and Ran. All cells use GTPases to regulate the delivery of amino acids to the ribosomeduring protein synthesis, but eukaryotes, with their complex and compartmentalized environment, have exploited the versatility of GTPases to a much greater extent. The roles of two further families of GTPases in protein localization and protein tanslocation are discussed in chapter 8. Chapter 9covers the huge amount of structural data accumulated for all families of GTPases and the proteins with which they interact. The final chapter describes the modification of GTPases by numerous bacterial toxins. It is not surprising, therefore, that GTPases have become a centre of attention forthose studying the control of proliferation, differentiation, cell polarity, cell movement and vesicle and protein trafficking. GTPases: Frontiers in Molecular Biology provides a complete guide to this area and should be essential reading for cell and molecular biologists, biochemists andgeneticists interested in these contemporary problems.