Lectin-receptor interactions in liposomes.

The major sialoglycoprotein of mammalian erythrocytes has been incorporated into phosphatidylcholine membranes to generate a model system, glycoprotein-liposomes. Electron microscopic examination revealed these structures to be vesicles, approximately 300 A in diameter. An aqueous compartment inside the glycoprotein-liposomes has been identified by trapped volume studies with [14C]sucrose. These glycoprotein-liposomes were found to interact with the lectins, wheat germ agglutinin, and phytohemagglutinin, to form aggregates of mainly unfused vesicles. The aggregation process has been studied by electron microscopy, 90 degrees light scattering, and differential ultracentrifugation analysis. Hapten inhibitors of the lectins were found to inhibit the lectin-induced aggregation of the glycoprotein-liposomes. Binding of 125I-labeled wheat germ agglutinin to glycoprotein-liposomes was studied by differential ultracentrifugation. Hapten inhibitors of wheat germ agglutinin were also found to inhbit the binding of 125I-labled wheat germ agglutinin to the glycoprotein-liposomes. The characteristics of the lectin interactions with glycoprotein-liposomes appeared to be phenomenologically similar to lectin-cell interactions.