GTPases in protozoan parasites: Tools for cell biology and chemotherapy

Small G proteins belong to a superfamily of GTPases related to the protoonc ogene ras, and function as master control elements for a range of cellular functions. This ability is related to their low rate of substrate turnover; GTPases catalyse the conversion of GTP to GDP, but with a rate in the orde r of one substrate per second, orders of magnitude slower than 'good' enzym e catalysis, but placing the reaction into the temporal frame of many cellu lar processes including signal transduction, cytoskeletal reorganization an d vesicle trafficking. In this article, Mark Field, Bassam Ali and Helen Fi eld describe some recent advances in G-protein studies in the parasite fiel d, concentrating on the protozoan parasites. Because of their numerous role s in cell biology, understanding parasite G proteins has great potential fo r increasing our knowledge of parasite cellular physiology, as well as prov iding important inroads into vital processes for potential therapeutic expl oitation.