An increase of calcium/manganese binding sites in cell ghosts associated with the acquisition of aggregative competence in Dictyostelium discoideum.

In Dictyostelium discoideum, the formation of multicellular aggregates represents the first morphogenetic event that leads ultimately to the construction of fruiting bodies. The altered adhesive properties of the cells can be demonstrated in ghosts derived from them which consist of largely intact membranes containing a few empty vesicles and exploded mitochondria but lacking nuclei, RNA, soluble cytoplasm and ATP [4]. A cofactor requirement for the aggregation of the ghosts can be satisfied by the following divalent cations: Ca²⁺, Mn²⁺, Zn²⁺ and Cu²⁺. In this paper it is shown that associated with the acquisition of aggregative competence is a 15–20-fold increase in the ghosts of sites capable of binding either Ca²⁺ or Mn²⁺ with relatively high affinity.