On the evolution of hexose transporters in kinetoplastid protozoans

PEREIRA, CA; SILBER, ARIEL

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2012 vol. 7 p. 36303 - 36303

1932-6203

Glucose, an almost universally used energy and carbon source, is processed throughseveral well-known metabolic pathways, primarily glycolysis. Glucose uptake isconsidered to be the first step in glycolysis. In kinetoplastids, a protozoan group thatincludes relevant human pathogens, the importance of glucose uptake in differentphases of the life cycles is well established, and hexose transporters have beenproposed as targets for therapeutic drugs. However, little is known about theevolutionary history of these hexose transporters. Hexose transporters contain anintracellular N- and C- termini, and 12 transmembrane spans connected by alternateintracellular and extracellular loops. In the present work we tested the hypothesis thatthe evolutionary rate of the transmembrane span is different from that of the wholesequence and that it is possible to define evolutionary units inside the sequence. Thephylogeny of whole molecules was compared to that of their transmembrane spansand the loops connecting the transmembrane spans. We show that the evolutionaryunits in these proteins primarily consist of clustered rather than individualtransmembrane spans. These analyses demonstrate that there are evolutionaryconstraints on the organization of these proteins; more specifically, the order of thetransmembrane spans along the protein is highly conserved. Finally, we defined asignature sequence for the identification of kinetoplastid hexose transporters.