β-linked N-acetylgalactosamine residues present at the nonreducing termini of O-linked oligosaccharides of a cloned murine cytotoxic T lymphocyte line are absent in a Vicia villosa lectin-resistant mutant cell line

The O-linked oligosaccharides of the cloned, murine cytotoxic T cell line B6.1.SF.1 were compared with the corresponding oligosaccharides from a Vicia villosa lectin-resistant mutant of B6.1.SF.1 called VV6 (Conzelmann, A., Pink, R., Acuto, O., Mach J.P., Dolivo, S., and Nabholz, M. (1980) Eur. J. Immunol. 10, 860-868). The VV6 mutant cells are deficient in binding sites for this GalNAc-specific lectin. Cells were grown in the presence of [³H]glucosamine and [³H]galactose to label the glycoproteins, and the desialyzed, alkaline borohydride-released oligosaccharides were isolated and characterized. The VV6 cells contained a series of O-linked oligosaccharides ranging in size from a disaccharide to a pentasaccharide. These were composed of galactose, N-acetylglucosamine, and N-acetylhexosaminitol, the latter sugar being derived from the reducing terminus. The predominant oligosaccharide had the partial structure GalβGlcNAcβ-(Galβ)-N-acetylhexosaminitol. In contrast, the analogous oligosaccharides of the parental cells contained additional β-linked GalNAc residues located at nonreducing termini. The smallest of these had the structure GalNAcβ1,4Galβ-N-acetylhexosaminitol. Neither cell line contained significant amounts of terminal GalNAc linked to Ser/Thr which is the main binding site for the V. villosa B₄ lectin on the Tn erythrocytes (Tollefsen, S.R., and Kornfeld, R. (1983) J. Biol. Chem. 258, 5172-5176). These findings suggest that the major binding sites for the V. villosa lectin on the parental cytotoxic T cell line consist of structures containing β1,4-linked GalNAc residues at the nonreducing ends of conventional O-linked structures. The VV6 cells lack these β-linked GalNAc residues, and this may account for their deficiency of V. Villosa lectin-binding sites. In the following paper (Conzelmann, A., and Kornfeld, S. (1984) J. Biol. Chem. 259, 12536-12542), we demonstrate that the VV6 cells are missing the N-acetylgalactosaminyltransferase that is responsible for the synthesis of these unusual oligosaccharides.