Molecular Organization of Cell Membranes Isolated from Myxamoebae of Cellular Slime Mold, Dictyostelium discoideum

II. Reassociation of Membrane Subunits

Abstract

Reassociation of 7S lipoprotein subunits and 3.3S protein subunits obtained from the cell membrane of vegetative myxamoebae of Dictyostelium discoideum was investigated with electron microscopy, turbidometry and sedimentation.
7S subunits reassociate into five kinds of aggregates; i.e., unit membrane structure, thick membrane of about twice as thick as that of the unit membrane, filamentous structure, partial aggregates and random aggregates. The proportion of various aggre-gates depended on the conditions for reassociation. The rate of subunit reassociation, hydrogen ion concentration, temperature, metal ion concentration, the valence of metal ion and the presence of substances such as urea influenced the subunit interaction and the morphology of the product.
Lipid-free protein subunits of the membrane reassociated into membrane structure by going through stages of intermediate aggregates, filaments and then side-by-side aggregation of filaments.