Localization of glycosyl transferases in plasma membranes from Dictyostelium discoideum

Abstract

Crude membranes from vegetative and aggregation competent cells of Dictyostelium discoideum Ax 2 were separated by a combination of differential and sucrose gradient centrifugation. A fraction mainly containing plasma membranes could be isolated. The high degree of purity was demonstrated by electron microscopy and by the presence of marker enzymes typical for the plasma membrane and the absence of enzymes characteristic for other subcellular compartments. Furthermore surface labelling with radioactive 1--fluoro--2,4--dinitrobenzene--14C and cAMP binding capacity were introduced as plasma membrane markers. In the pure plasma membrane fraction endogenous activities of D--mannosyl-, D--glucosyl- and N--Acetyl--D--glucosaminyl--transferases were present. The activities in plasma membranes of aggregation competent cells were up to thirty times higher than in membranes isolated from vegetative cells.

Topography of the Dictyostelium discoideum plasma membrane: analysis of membrane asymmetry and intermolecular disulfide bonds

“…Pc 43.2 which was observed only in cytoplasmic face labeled PM is probably radiolabeled actin. Sievers et al (1978) have reported glycosyl transferase activities in the PM of vegetative Dictyostelium cells; nothing is known about the enzyme(s) itself.…”