We have developed two improved methods: (1) a procedure for coupling 125Iodine to ConcanavalinA (ConA) that yields intensely labeled and fully active lectin; (2) a procedure that allows studies of lectin binding to be carried out with a minimum of non-specific binding to reaction vessels. We found that BALB/c 3T3 cells, SV3T3 cells, and human red blood cells have 1.3 × 107, 1.5 × 107, and 2.2 × 106 ConA binding sites/cell. More than 99.5% of the radioactivity in the samples counted was associated with the cells; background radioactivity, in the absence of cells, was negligible. We also found that although α-methylmannopyranoside (α-MM) prevented almost all of the ConA from binding to cells, when ConA had first been allowed to bind, α-MM removed only 60 to 80% of the bound ConA. In addition, even after the removal of a portion of bound lectin by α-MM, most, if not all, of the remaining cell-associated ConA was coupled to the plasma membrane.
All Science Journal Classification (ASJC) codes
- Cell Biology