Rapid, transient methylation of four proteins in aggregative amoebae of Dictyostelium discoideum as a response to stimulation with cyclic AMP.

In Dictyostelium discoideum, extracellular cAMP induces chemotaxis and cell aggregation. Suspensions of cAMP-sensitive cells are shown to respond to a 10(-6) M cAMP-pulse with increased methylation of 4 proteins with app. Mr 110000, 46000, 28000 and 16000. The Mr 110000 and 28000 proteins show a triphasic response with maxima 15, 60 and 150-180 s after stimulation. The responses of the Mr 46000 and 16000 proteins are monophasic, maxima being reached 3 and 15 s after stimulation, respectively. Optimal responses of methylation are observed over 10(-7) - 10(-6) M cAMP. The methylation reaction may be involved in the processing of the chemotactic signal.