Cyclic membrane changes in animal cells: transformed cells permanently display a surface architecture detected in...

A membrane site exposed only during mitosis in normal 3T3 cells, but exposed in all polyomavirus transformed 3T3 (Py3T3) cells, has been detected The site was identified by the specific binding of a wheat-germ agglutinin conjugated with fluorescein isothiocyanate. The receptor site has been studied previously. It binds wheat-germ agglutinin, causing the selective agglutination of Py3T3 cells, but not normal 3T3 cells. A short treatment with low concentrations of trypsin exposes cryptic sites in 3T3 cell membranes; this permits agglutination of these cells. The experiments reported here indicate that these sites normally are exposed during a brief period of the cell cycle for 3T3 cells. Specific hapten inhibitors of agglutination also inhibit the binding of the conjugated agglutinin and prevent fluorescence.