CHARACTERIZATION OF GLUCOSE-TRANSPORT AND CLONING OF A HEXOSE TRANSPORTER GENE IN TRYPANOSOMA-CRUZI

A gene from Trypanosoma cruzi, TcrHT1, which encodes a member of the g lucose transporter superfamily has been cloned. The gene is similar in sequence to the T. brucei hexose transporter THT1 and the Leishmania transporter Pro-1 and is present in the T. cruzi genome as a cluster o f at least eight tandemly reiterated copies. Northern blot analysis re vealed two mRNA transcripts which differ in size with respect to their 3' untranslated regions. When injected with in vitro transcribed TcrH T1 mRNA, Xenopus oocytes express a hexose transporter with properties similar to those of T. crud. Glucose transport in T. cruzi is mediated via a carrier with unique properties when compared with the other glu cose transporters already characterized among the Kinetoplastida. It i s a facilitated transporter with a high affinity for D-glucose (K-m = 84.1 +/- 7.9 mu M and V-max = 46 +/- 9.4 nmol/min per mg of protein) t hat shares with other kinetoplastid hexose transporters the ability to recognize D-fructose, which distinguishes these carriers from the hum an erythrocyte glucose transporter GLUT1.