DEVELOPMENTALLY REGULATED INHIBITOR OF AGGREGATION IN CELLS OF DICTYOSTELIUM-DISCOIDEUM

The soluble fraction of exponential phase cells inhibits differentiation and aggregation in cells of Dictyostelium discoideum. Lower inhibitor activities have been found in aggregation-competent cells than in growth phase cells. The inhibitor has a molecular weight between 1000 and 1300, as determined on Sephadex G-25. It is stable against heat, alkali and acid, and resists periodate and pronase treatment. Three biochemical processes accompanying cell differentiation have been shown to be blocked by the inhibitor: the increase of adenylyl cyclase activity, the formation of EDTA-stable cell contacts, and the release of an inhibitor of cyclic-AMP phosphodieterase into the extracellular medium. © 1979.