FUNCTIONAL EXPRESSION AND SUBCELLULAR-LOCALIZATION OF A HIGH-K-M HEXOSE TRANSPORTER FROM LEISHMANIA-DONOVANI

We have used expression in Xenopus oocytes to characterize a new hexos e transporter from the parasitic protozoan Leishmania donovani. This t ransporter utilizes the hexoses glucose, fructose, and mannose as subs trates. A substrate saturation curve for 2-deoxy-D-glucose reveals a v ery high K-m, estimated to be approximately 150 mM. Immunolocalization of the protein with an antibody directed against the COOH terminus in dicates that the transporter is present primarily in the parasite plas ma membrane but is not detectable in the flagellar membrane. Since thi s protein is expressed in the insect stage promastigotes but not in th e intracellular amastigotes, it may be specialized to function followi ng an insect sugar meal when the concentrations of sugars surrounding the parasite are high.