Structure and expression of a tandem gene pair in Leishmania donovani that encodes a protein structurally homologous to eucaryotic cation-transporting ATPases.

Abstract

Leishmania amastigotes do not appear to alter the phagolysosomal pH (27), but rather possess membrane transport systems that are designed to exploit the acidic environment provided by the lysosome. Adaptation of amastigotes to high extracellular proton concentrations is strikingly evidenced by their metabolic behavior. Amastigotes optimally respire, metabolize glucose, and incorporate thymidine, uridine, and proline when bathed in medium between pH 4.0 and 5.5 (22). pH levels comparable to those within phagolysosomes. The effect of extracellular protons on the metabolic activity of amastigotes is probably due to increased nutrient transport through proton-coupled symporters, such as the glucose transporter (37,38). Proton influx is countered in both amastigotes and promastigotes by a plasmatemma proton pump, which is capable of generating a proton gradient across the plasma membrane (37; T. Glaser and A. Mukkada, personal communication). While the possible existence of other cation pumps has not been rigorously excluded, available evidence suggests that L. donotiani may rely solely on a proton pump to drive the uptake of nutrients and to regulate ion flow (37

Lack of Abundance of Cytoplasmic Cyclosporin A-binding Protein Renders Free-living Leishmania donovaniResistant to Cyclosporin A

“…Second, the predicted translation initiation is preceded by a sequence closer to the eucaryotic translation initiation signal (39). Third, the occurrence of the multiple polypyrimidine stretches, typical of all the Leishmania-encoded genes, was clearly prevalent upstream of the predicted translation initiation site, and finally, the sequence upstream of the predicted translation site exhibited only 60% preference for G/C at the wobble position, far lower than the high G/C bias (Ն80%) invariably observed in most genes, including LdCyP, cloned from L. donovani (18,40,41).…”

Trypanosoma cruzi H+-ATPase 1 (TcHA1) and 2 (TcHA2) Genes Complement Yeast Mutants Defective in H+ Pumps and Encode Plasma Membrane P-type H+-ATPases with Different Enzymatic Properties

“…Reduction in absorbance of acridine orange using the wavelength pair 493-530 nm indicates acidification of vesicles in the preparation. This acidification was reversed by the addition of 10 mM NH 4 Cl, which, being a weak base, accumulates in the vesicles and neutralizes (Fig. 8, traces b-d, respectively).…”

Multidrug resistance in Leishmania donovani is conferred by amplification of a gene homologous to the mammalian mdr1 gene.

“…Moreover, the vinblastine-resistant cells were also cross-resistant to puromycin (Fig. iB) (22), taking into consideration the codon bias previously observed for leishmanial housekeeping genes (6,9,19,23,38,56). Only reactions containing both primers, template L. enriettii DNA, and Taq polymerase generated amplified sequences.…”

“…The degeneracy of the primers was based on the codon bias previously observed for nuclear genes in Leishmania species (6,9,19,23,38,56).…”