Localization of sugar-binding proteins in Trypanosoma cruzi using gold-labeled neoglycoproteins.

Neoglycoproteins labeled with colloidal gold particles were used for the ultrastructural localization of sugar-binding sites in epimastigote, amastigote and trypomastigote forms of Trypanosoma cruzi. Binding sites for N-acetyl-D-glucosamine and D-galactose were seen on the surface of about 80% and 5 to 10% of the trypomastigote forms, respectively. They were inhibited by addition of the respective monosaccharides to the incubation medium. Binding sites for D-mannose were not observed in trypomastigotes. No labeling of the surface of amastigote and epimastigote forms was observed with the neoglycoproteins which bind to N-acetyl-D-glucosamine, D-galactose and D-mannose-binding sites. Labeling of the nucleus and the kinetoplast with the neoglycoprotein which recognizes N-acetyl-D-glucosamine binding sites was observed. The results obtained are discussed in relation to the possible role which surface sugar binding sites play in the process of T. cruzi-host cell interaction.