Cell surface alterations of avian sarcoma virus B77-and 3,4-benzo(a)pyrene-transformed rat fibroblasts. II. Cell surface glycoproteins characterized by two-dimensional electrophoresis.

Cell surface proteins of avian sarcoma virus B77-, 3,4-benzo(a)pyrene- and spontaneously transformed rat fibroblasts were tritium-radiolabeled by mild periodate oxidation followed by tritiated sodium borohydride reduction and by galactoseoxidase/NaB3H4 technique. Radiolabeled cell surface sialoglycoproteins were analyzed by electrophoresis under denaturing conditions (SDS-PAGE), or by two-dimensional electrophoresis (isoelectric focusing, SDS-PAGE). Following major glycoproteins were quantitatively decreased on all examined transformed cells: a 220k glycoprotein with pI of approximately 6.2, a 180k glycoprotein with pI of approximately 6.0-6.2, a 110k glycoprotein (pI 6.2). A series of further sialoglycoproteins was quantitatively increased on all examined transformed cells, as follows: a markedly increased 70k glycoprotein (pI approximately 4.8) and a 120k glycoprotein (pI 5.0-5.2) increased more markedly on onco-virus-transformed and spontaneously transformed cells. Further sialogalactoprotein (28k, pI 5.8) was visualized as increased on all examined transformed cells only by galactoseoxidase/NaB3H4 technique. A 70k sialoglycoprotein was immunoprecipitated from transformed cells by the immune serum against Friend murine leukemia virus envelop glycoprotein gp70 and, to a markedly lesser extent, from untransformed cells. A similar glycoprotein, together with an another 120k glycoprotein were precipitated from transformed cells and to a minor extent from untransformed cells also by an antiserum against endogenous rat type-C virus.