Localization of the Plasmodium falciparum PfNT1 nucleoside transporter to the parasite plasma membrane

Nutrient transporters play critical roles in parasite metabolism, but the m embranes in which they reside have not been clearly defined. The transport of purine nutrients is crucial to the survival of the malaria parasite Plas modium falciparum, and nucleoside transport activity has been associated wi th a number of different membrane components within the parasitized erythro cyte. To determine the location of the PfNT1 nucleoside transporter, the fi rst component of the nucleoside permeation pathway to be studied at the mol ecular level in P. falciparum (Carter, N. S., Ben Mamoun, C., Liu, W., Silv a, E. O., Landfear, S. M., Goldberg, D. E., and Ullman, B. (2000) J. Biol. Chem. 275, 10683-10691), polyclonal antisera against the NH2-terminal 36 am ino acids of PfNT1 were raised in rabbits. Western blot analysis of parasit e lysates revealed that the antibodies were specific for PfNT1 and that the level of PfNT1 protein in the infected erythrocyte is regulated in a stage -specific fashion. The amount of PfNT1 polypeptide increases dramatically d uring the early trophozoite stage and reaches its maximal level in the late trophozoite and schizont stages. Deconvolution and immunoelectron microsco py using these monospecific antibodies revealed that PfNT1 localizes predom inantly, if not exclusively, to the plasma membrane of the parasite and not to the parasitophorous vacuolar or erythrocyte membranes.