LdAAP3 response to deprivation is specific to arginine.
Initial rates (up to 3 minutes) of arginine transport was determined in mid log-phase axenic L. donovani promastigotes (A) and amastigotes (B). Parasites (0.5-1X107 cells/ml) were incubated for 2 hours in medium 199 (pH 7 and 5.5 for promastigotes and amastigotes, respectively) with or without the amino acids indicated in the X-axis of each panel. Subsequently, cells were washed twice in EARL's salt solution and subjected to arginine transport assays using the rapid filtration technique as described in Materials and Methods. Radiolabeled amino acids were added at medium 199 concentrations. Values are the mean±S.D. of three independent repeats. Transport rate at 100% was 0.4±0.05 nmol/min/1X108 cells in promastigotes and 0.8±0.1 nmol/min/1X108 cells in amastigotes.