Identification and partial characterization of plasma membrane polypeptides of Trypanosoma brucei (original) (raw)
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Receptor-mediated endocytosis in the bloodstream form of Trypanosoma brucei
The Journal of protozoology, 1987
The uptake of various host plasma proteins by the bloodstream form of Trypanosoma brucei was studied both biochemically, using radiolabeled proteins, and with the electron microscope, using colloidal gold particles as molecular tracers onto which plasma proteins had been adsorbed. Total plasma proteins and serum albumin were taken up by a mechanism of fluid endocytosis with low clearance (0.1 microliter [mg cell protein]-1 h-1), while low-density lipoprotein (LDL) and transferrin were taken up by a receptor-mediated process with a clearance of two to three orders of magnitude higher than that of serum albumin. Binding prior to uptake of LDL and transferrin was saturable, depended on the presence of Ca2+, and the labeled ligand could be displaced by the homologous but not by heterologous protein. Binding of gold-labeled proteins was seen only to the membrane of the flagellar pocket and not elsewhere on the plasma membrane. After 1 h of incubation at 30 degrees C with gold-labeled LDL...
Trypanosoma cruzi: binding of parasite antigens to mammalian cell membranes
Parasite Immunology, 1980
Muscle and neuronal cell lines were infected with Trypunosoma cruzi and stained for the presence of parasite antigens by immunofluorescence. Up to 72 h post infection, fluorescence was limited to the intracellular amastigote stages. After the release of parasites, at about 96 h, fluorescence was also associated with the membranes of normal and infected cells. This finding was reproduced by passive sensitization of uninfected cells using amastigote antigens at protein concentrations as low as 10 pg ml-I. Intriguingly, although both normal and transformed cells of muscle and nervous tissue origin adsorbed significant quantities of antigen, lymphocytes and erythrocytes failed to show any detectible uptake.
Proceedings of the National Academy of Sciences of the United States of America, 1976
Intact, washed Trypanosoma lewisi bloodstream forms, isolated from rats, were agglutinated specifically by antisera against rat whole serum, albumin, alpha2-macroglobulin, and IgG. However, trypsinized bloodstream and intact culture forms lacking surface coat were not agglutinated by these antisera. Trypsinized bloodstream forms, incubated in dilute rat or heterologous host serum proteins, were agglutinated with specific antisera. The characteristic surface coat of intact bloodstream forms was absent from trypsinized cells; however, trypsinized and serum-incubated bloodstream forms reacquired a surface coat similar to that of intact cells. Gel-diffusion and immunoelectrophoretic results showed that rat albumin, alpha2-macroglobulin, and IgG were present in the surface coat of bloodstream forms. Results of quantitative rocket immunoelectrophoresis demonstrated that the adsorbed rat serum proteins constituted by weight about 5% of the trypanosome total surface coat protein.
The Journal of Eukaryotic Microbiology, 2002
The plasma membrane potential (AT) of procyclic and bloodstream trypomastigotes of Trypanosoma brucei was studied using the potentiometric fluorescent dye bisoxonol. Our results suggest that a proton pump plays a significant role in the regulation of A T in procyclic and bloodstream forms, as evidenced by depolarization of the plasma membrane by H+-ATPase inhibitors (e.g. dicyclohexylcarbo-diimide, N-ethylmaleimide, diethylstilbestrol, and bafilomycin A,). In bloodstream stages the plasma membrane was significantly depolarized by ouabain only when the cells were incubated in sodium-rich buffers indicating that a sodium pump was being inhibited. In contrast, ouabain had no effect on the A T of the procyclic stages in a sodium-rich buffer. However, it induced an additional significant depolarization in these stages when their plasma membrane was already partially depolarized by the H+-ATPase inhibitor dicyclohexylcarbo-diimide, indicating the presence of an ouabain-sensitive sodium pump whose activity is masked by the H+-ATPase. Unlike procyclic forms, the A T of bloodstream-stage trypomastigotes was markedly sensitive to extracellular Na+ and K+ concentrations. Thus, there are significant differences between procyclic and blooodstream forms in the maintenance of-the A* and in their permeability to cations.
Biochemistry, 1988
Secondary structure determinations have been carried out on two antigenically related variant surface glycoproteins (VSG's) from Trypanosoma brucei, WaTat 1.1 and WaTat 1.12. The two molecules, which bear highly homologous amino-terminal sequences, showed subtle differences in their circular dichroism (CD). Computer analysis revealed that the contribution of a helix to the secondary structure of the VSG's was 49% for WaTat 1.1 and 52% for WaTat 1.12. Unfolding studies using guanidine hydrochloride suggested that the WaTat 1.12 VSG was slightly more resistant than WaTat 1.1 VSG to the effect of this reagent.