1. A method which allows the characterization of lectin-binding components is described. This method should be useful in defining the nature and heterogeneity of these components in cell membranes. 2. The method, which we have used on erythrocyte “ghosts”, involves the fixation of “ghost” components after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and incubation with purified 125I-labelled lectins. 3. Each of the four lectins used shows an individual pattern of reactivity towards “ghosts” components. Band 3, the major membrane-penetrating glycoprotein, is bound by the lectins from Ricinus communis and Phaseolus vulgaris (phytohaemagglutinin) and by concanavalin A. The major erythrocyte sialoglycoprotein is bound by the lectins from R. communis, P. vulgaris and Maclura aurantiaca. 4. Three of the lectins displays binding for other membrane components, some of which are not demonstratable by conventional protein- and carbohydrate-staining techniques.
