Surface carbohydrates of hamster fibroblasts. II. Interaction of hamster NIL cell surfaces with Ricinus communis lectin and concanavalin A as revealed by surface galactosyl label.

When hamster fibroblasts (NIL) were treated with galactose oxidase followed by reduction with tritiated borohydride (GAHMBERG, C. G. AND HAKOMORI, S. (1973) J. Biol. Chem. 248, 4311; STECK, T. L., AND DAWSON, G. (1974) J. Biol. Chem. 249, 2135), two major galactoprotein labels were detected on the cell surface: "galactoprotein a" (apparent molecular weight 200,000) and "galactoprotein b" (apparent molecular weight 130,000). The labeling in galactoprotein a of NIL cells was greatly suppressed by pretreating cells with a high concentration of Ricinus communis lectin or concanavalin A, whereas the label in it was greatly enhanced with a low concentration of the lectins. The label in galactoprotein b of NIL cells was less affected by pretreatment with lectins. In NILpy cells the label in galactoprotein a was absent and the lable in galactoprotein b was enhanced by pretreating cells with lectins at low concentrations, but it was suppressed at high concentrations. The results indicate that NIL cells mainly interact with the lectins through galactoprotein a, whereas NILpy cells interact with the lectins through galacto-protein b. After treatment with lectins, the glycolipids of normal NIL cells, but not NILpy cells, became exposed as evidenced by enhanced labeling, possibly because of "clustering" of glyco-proteins. These results support the view that specific, well defined glycoproteins are the binding sites for lectins, and that these interacting glycoproteins are qualitatively different in normal and transformed cells.