Effect of RhoA inactivation by C3 exoenzyme on agonist-induced affinity modulation of platelet α_IIbβ₃. Washed platelets were incubated with vehicle buffer (“No C3”) or C3 exoenzyme as in Fig 3. Cells were then diluted with incubation buffer and the affinity state of α_IIbβ₃ was assessed by flow cytometry using FITC-PAC1. PAC1 binding was expressed as a percentage, 100% being arbitrarily assigned to the maximal response for the “No C3” control sample that had been paired with the experimental sample containing 200 μg/mL of C3 exoenzyme. Data represent the means ± SEM of three experiments.