Signalling the genome: the Ras-like small GTPase family of trypanosomatids.

The genomes of the three principle experimental-model species of Kinetoplastida -Trypanosoma brucei brucei, Trypanosoma cruzi and Leishmania major - are now complete, providing both a milestone for trypanosome biology and an opportunity to consider a multitude of questions at the genome level. Of the >40 members of the Ras-like GTPase family in T. brucei, at least 30 are involved in intracellular transport, whereas fewer than eight are likely to have a classical role in signal transduction. There are no true members of the Ras or Rho subfamilies but divergent Ras- or Rho-like GTPases are present, suggesting that signalling mechanisms in trypanosomatids are highly unusual. Comparisons of T. brucei with T. cruzi and L. major indicate a high degree of conservation among the species. These analyses provide a framework for the functional investigation of small-GTPase-mediated signalling processes in trypanosomes.