CONCANAVALIN A-INDUCED AGGLUTINATION AND BINDING OF CON A TO THE DIFFERENTIATING CELLS OF DICTYOSTELIUM DISCOIDEUM

Abstract

Changes in agglutinability of D. discoideum cells with Concanavalin A (Con A) during the course of development were investigated. The agglutinability of the cells was assayed under conditions where no spontaneous cell agglutination occurred. There was a progressive decrease in Con A-induced agglutinability during development: a decrease to half from exponentially growing cells to preaggregation cells, and a decrease to a sixth in disaggregated slug cells. Pronase-BAL [2,3 dimercapto-1-propanol] treatment of preaggregation cells did not enhance their agglutinability with Con A. The amounts of sites available for binding Con A were determined with preaggregation and slug cells. Cells were incubated at 4.degree. C and in the presence of NaN3 to avoid possible endocytosis of Con A. No significant differences in numbers of Con A-binding sites per unit area of cell surface was detected among preaggregation cells, those treated with pronase and BAL and cells disaggregated from slugs by similar treatment. It was concluded that the decrease in Con A-induced agglutinability during development is not attributable to changes in the numbers of Con A-binding sites.