John E. Geltosky

Glycoproteins of the plasma membrane of dictyostelium discoideum during development

Differential binding of 125I-Con A to whole cells throughout the life cycle of dictyostelim discoideum indicates that the appearance of Con A binding proteins on the plasma membrane is under developmental regulation. Con A-Sepharose affinity chromatography of radio-iodinated plasma membrane preparations, followed by analysis with SDS-PAGE, revealed that there are at least 15 Con a binding proteins associated with the surface of 0 hr cells. Between 6 and 18 hr of development, the relative intensity of one of the bands, which corresponds to a protein of molecular weight of 150,000 daltons, increases dramatically.

A glycoprotein involved in aggregation of D. discoideum is distributed on the cell surface in a nonrandom fashion favoring cell junctions

We studied the distribution on the cell surface of a glycoprotein (gp150) involved in the aggregation process of Dictyostelium discoideum. Using immunohemocyanin labeling of intact aggregates and visualization by scanning elecron microscopy (SEM), we found a distribution gradient of gp150 wherein the concentration was enriched at or near sites of cell contact. When the distribution of gp150 on the cell surface was examined with immunoferritin and transmission electron microscopy (TEM), we found that gp150 was closely associated with the plasma membrane.