FIG. 3.

Effect of K⁺ depletion and chlorpromazine treatment on tyrosine phosphorylation of cdc2 in HdCDT-treated cells. Cells were depleted of K⁺ as described in Materials and Methods and treated with HdCDT; samples were prepared 24 h after toxin exposure. For chlorpromazine treatment, cells were preincubated with chlorpromazine (25 μg/ml, 1 h), treated with HdCDT, and postincubated for 8 h with 10 μg of the drug per ml. Intoxication with DT and measurement of DT activity (inset) were performed as described in Materials and Methods. Error bars indicate standard deviations.