Rac activation is facilitated by ROS signaling. (A) PBD-PAK pulldown assays were used to quantify GTP-bound Rac1 in unstimulated neutrophils and cells stimulated for 1 minute with fMLP (1μM). fMLP induced an increase in Rac1 activity, which was attenuated by 15 minutes of preincubation with 10mM NAC. (B) The average ± SD of 3 independent Rac-GTP pulldown assays are presented in the bar diagram. (C) Active Rac1 was pulled down with the PBD-PAK from gp91^−/− neutrophils and control cells (C57/BL57) after stimulation with fMLP (1μM) and/or H₂O₂ (50μM). Where indicated, cells were pretreated with Trolox (100μM).