| Abstract: | Membrane glycoprotein biosynthesis of ascites hepatoma cells is followed by 14C]glucosamine and 3H]leucine incorporation into cells in culture. The rate of incorporation is strongly increased by the addition of Robinia lectin in culture medium. Labeled glycoproteins are released from lectin stimulated and non-stimulated cells by trypsin digestion. Studies of labeled trypsinates on sodium dodecyl sulfate gel electrophoresis and Sephadex G-200 filtration exhibit two fractions both labeled with 14C]glucosamine and 3H]leucine and having different molecular weights, one over 200000 and the other about 2000. Identical results are obtained when external membrane glycoproteins are solubilized by sodium deoxycholate. Comparison of surface glycoproteins isolated by trypsinization from control cells labeled with 3H]-glucosamine and from lectin stimulated cells labeled with 14C]glucosamine displays no significant qualitative differences between glycoprotein fractions released from both cell groups. |
