ADP-ribosylation of RhoA in platelets by C3 exoenzyme. In (A) washed platelets were incubated for 4 hours at 37°C in the presence of vehicle buffer (“No C3”) or C3 exoenzyme. The platelets were then washed and subjected to α(³²P)ADP-ribosylation assay as described in Materials and Methods. In (B) the solid bars represent the means ± SEM of three experiments.