A specific glycoprotein as the target site of adhesion blocking Fab in aggregating Dictyostelium cells

During the acquisition of aggregation competence a new antigen appears on the surface of Dictyostelium cells. Univalent antibody fragments (Fab) against this antigen render the cells unable to form the specific type of cell adhesion which is characteristic of aggregating cells. This membrane constituent has been purified and identified as a concanavalin A-binding glycoprotein present at about 2 X 10(5) copies per cell.