Selective loss of wheat germ agglutinin binding to agglutinin resistant mutants of Chinese hamster ovary cells

The binding of ¹²⁵I-labeled wheat germ agglutinin (WGA) to parental and three distinct WGA-resistant Chinese hamster ovary cell lines possessing modified cell surface carbohydrate structure has been examined over a 10⁶-fold range of WGA concentrations. The Scatchard plot for WGA binding to parental cells was complex and exhibited positively cooperative binding at the high affinity sites. One of the WGA-resistant mutants [Wga(RIII)] was apparently not altered in its WGA-binding ability compared with parental cells. However, two of the WGA-resistant lines [Wga (R I) and Wga (R II)] had distinct alterations in their WGA-binding properties specific to certain regions of the binding curve. Neither appeared to be affected in either the highest or lowest affinity regions of the binding curve. Thus, lectin resistant cell mutant altered in specific lectin-binding sites at the cell surface provide a direct approach to analysis of the complex binding parameters that characterize the interaction of WGA with the plasma membrane.