Evidence that the major cell suface glycoprotein of the TA3-Ha carcinoma contains the Vicia graminea receptor sites.

The Vicia graminea lectin receptor of the nonstrain-specific TA3-Ha mammary carcinoma ascites cell of the strain A mouse was shown to be predominantly or exclusively on a large mucin-type surface glycoprotein. TA3-Ha cells adsorbed the lectin in amounts equivalent to 5-9 mg of this glycoprotein/10-9 cells, which was 100-400 times greater than by the strain-specific TA3-St cell, employed as a control. Release of sialic acid by incubation with neuraminidase increased the adsorptivity of the TA3-Ha cell three to fourfold and of the TA3-St cell six- to ten fold. Proteolysis of TA3-Ha cells released into the supernatant solutions approximately the same amount of inhibitory activity, equivalent to approximately 5 mg of the glycoprotein and only 10 per cent of the original adsorptivity remained on the cells. By contrast, TA3-St cells released no detectable inhibitory activity into the medium when subjected to similar proteolysis, even after neuraminidase treatment. Upon fractionation of released material on gel columns, high-molecular weight material and activity were found in the same fractions, but purified samples differed significantly in specific activity and carbohydrate composition. Heterogeneity in the carbohydrate moieties of the macromolecules was further demonstrated by incubation of these samples with neuraminidase, which enhanced their inhibitory activities from two- to tenfold.