Carbohydrate complexity of the mouse thymocyte Thy-1 glycoprotein as demonstrated by lectin affinity and isoelectric focusing.
The Thy-1 glycoprotein of mouse thymocytes was analysed with regard to the properties of its carbohydrate part. Of the different lectins tested, partial binding of Thy-1 from membrane extracts was found to Lens culinaris agglutinin (approximately 50%) and wheat germ agglutinin (approximately 25%). In contrast, concanavalin A bound all Thy-1. The results indicate that there is considerable microheterogeneity in the oligosaccaride chains within the Thy-1 population. Thy-1 was purified from thymocyte membrane extracts by concanavalin A affinity chromatography and gel filtration. The purified preparation revealed, on analysis by isoelectric focusing, at least six charge variants (isoelectric points ranging from approximately 5-9). These variants were isolated, treated with neuraminidase and tested for lectin binding and isoelectric point. It was shown that the charge heterogeneity was due to different amounts of sialic acid; even the most basic form contained at least one sialic acid residue. Furthermore, it was concluded that the degree of sialylation was not correlated to the lectin-binding properties. Analysis of Thy-1 from surface 125I-labelled thymocytes showed that the purified preparation was representative in its complexity of the Thy-1 glycoprotein exposed on the surface membrane. The possible biological implications of the findings are discussed.
D000818:Animals; D000954:Antigens, Surface / Q000302:isolation & purification*; D005260:Female; D006023:Glycoproteins / Q000302:isolation & purification*; D007525:Isoelectric Focusing; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification*; D051379:Mice; D008810:Mice, Inbred C57BL; D009439:Neuraminidase; D009844:Oligosaccharides / Q000032:analysis*; D011975:Receptors, Mitogen / Q000302:isolation & purification*; D018800:Thy-1 Antigens; D013950:Thymus Gland / Q000276:immunology*
D000954:Antigens, Surface; D006023:Glycoproteins; D008565:Membrane Proteins; D009844:Oligosaccharides; D011975:Receptors, Mitogen; D018800:Thy-1 Antigens; D009439:Neuraminidase