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Trypanosoma cruzi, the aetiological agent of Chagas' disease, is exposed to extremely different environment conditions during its life cycle, and transporters are key molecules for its adaptive regulation. Amino acids, and particularly arginine, are essential components in T. cruzi metabolism. In this work, a novel T. cruzi arginine permease was identified by screening different members of the AAAP family (amino acid/auxin permeases) in yeast complementation assays using a toxic arginine analogue. One gene candidate, TcAAAP411, was characterized as a very specific, high-affinity, l-arginine permease. This work is the first identification of the molecular components involved specifically in amino acid transport in T. cruzi and provides new insights for further validation of the TcAAAP family as functional permeases.

L-Cysteine and methionine are unique amino acids that act as sulfur donors in all organisms. In the specific case of Trypanosomatids, L-cysteine is particularly relevant as a substrate in the synthesis of trypanothione. Although it can be synthesized de novo, L-cysteine is actively transported in Trypanosoma cruzi epimastigote cells. L-Cysteine uptake is highly specific; none of the amino acids assayed yield significant differences in terms of transport rates. L-Cysteine is transported by epimastigote cells with a calculated apparent K(m) of 49.5 microM and a V(max) of about 13 pmol min(-1) per 10(7) cells. This transport is finely regulated by amino acid starvation, extracellular pH, and between the parasite growth phases. In addition, L-cysteine is incorporated post-translationally into proteins, suggesting its role in iron-sulfur core formation. Finally, the metabolic fates of Lcysteine were predicted in silico.

Aspartate is one of the compounds that induce the differentiation process of the non-infective epimastigote stage to the infective trypomastigote stage of the protozoan parasite Trypanosoma cruzi. l-aspartate is transported by both epimastigote and trypomastigote cells at the same rate, about 3.4 pmolmin(-1) per 10(7) cells. Aspartate transport is only competed by glutamate suggesting that this transport system is specific for anionic amino acids. Aspartate uptake rates increase along the parasite growth curve, by amino acids starvation or pH decrease. The metabolic fate of the transported aspartate was predicted in silico by identification of seven putative genes coding for enzymes involved in aspartate metabolism that could be related to the differentiation process.

Trypanosoma cruzi, the etiological agent of Chagas disease, uses arginine for several metabolic processes, including energy reserves management. In the present work, a novel low-affinity arginine transport system has been studied. Maximum velocity (97 pmol min(-1) per 10(7) cells), and an estimate for the apparent Km value (350 microM) of this arginine transporter, were 6-fold and 80-fold higher respectively, when compared with the previously described high-affinity arginine transport system. This transport activity seems to be H+ -mediated, presents a broad specificity by other amino acids such as methionine, and is regulated along the parasite growth curve and life cycle.