FIGURE 7. RacE is essential for maintaining cortical tension in Dictyostelium. The cortical tension of interphase cells in suspension culture was measured by the micropipet aspiration method. RacE null cells have a dramatic reduction in their cortical tension compared to wild-type cells. Ectopic expression of constitutively active racE (V20-racE) restores the tension of racE null cells to wild-type levels. A constitutively inactive racE protein (N25-racE) is ineffective in restoring cortical tension in racE null cells. Bars indicate mean ± standard deviation of 20 measurements.