FIG. 2.

Effects of excess amounts of mutant toxins on ACT-mediated intracellular cAMP accumulation in sheep erythrocytes. Sheep erythrocytes (5 × 10⁸/ml) were treated with mixtures containing wild-type (0.05 μg/ml) and mutant (0 to 5 μg/ml) toxins in TNC buffer at 37°C for 30 min. Intracellular cAMP was then extracted and measured as described in the text. Mean values and standard errors from triplicate assays are presented.