Novel motifs in amino acid permease genes from Leishmania.

Eight amino acid permease genes from the protozoan parasite Leishmania donovani (AAPLDs) were cloned, sequenced, and shown to be expressed in promastigotes. Seven of these belong to the amino acid transporter-1 and one to the amino acid polyamino-choline superfamilies. Using these sequences as well as known and characterized amino acid permease genes from all kingdoms, a training set was established and used to search for motifs, using the MEME motif discovery tool. This study revealed two motifs that are specific to the genus Leishmania, four to the family trypanosomatidae, and a single motif that is common between trypanosomatidae and mammalian systems A1 and N. Interestingly, most of these motifs are clustered in two regions of 50-60 amino acids. Blast search analyses indicated a close relationship between the L. donovani and Trypanosoma brucei amino acid permeases. The results of this work describe the cloning of the first amino acid permease genes in parasitic protozoa and contribute to the understanding of amino acid permease evolution in these organisms. Furthermore, the identification of genus-specific motifs in these proteins might be useful to better understand parasite physiology within its hosts.