Lentil lectin binding properties of the leucocyte common antigen from rat dividing and non-dividing thymocytes

The surface glycoproteins of rat large, mainly dividing, thymocytes and their small, non-dividing, progeny have been examined by labelling with 3H-sodium borohydride. A prominent glycoprotein component of apparent mol. wt. 150 K was labelled on both the cell types and by immunoprecipitation with a specific monoclonal antibody, was demonstrated to contain the leucocyte common antigen (LCA). The binding of this glycoprotein to Lens culinaris lectin (LcH) has been studied. Preliminary results obtained by different binding of ratiolabelled LcH to sodium dodecyl sulphate (SDS) solubilised crude plasma membrane from large and small thymocytes, fractionated by polyacrylamide gel electrophoresis (PAGE) indicated that a 150 K apparent molecular weight glycoprotein in the small cells bound radiolabelled LcH whereas virtually no binding of the lectin was observed in the 150 K region for large cells. However, by utilizing a different approach of lectin affinity chromatography on LcH-Sepharose 4B of solubilized NaB3H4 labelled membrane, followed by immunoprecipitation, we unequivocally showed that the 150 K labelled glycoprotein of both large and small cells was bound to LcH lectin and only eluted with the specific sugar alpha-methyl pyranoside (alpha-MP). The implications of these results is discussed.