It is well established that growth-factor-induced reactive oxygen species (ROS) 
act as second messengers in cell signaling. We have previously reported that 
betaPix, a guanine nucleotide exchange factor for Rac, interacts with NADPH 
oxidase 1 (Nox1) leading to EGF-induced ROS generation. Here, we report the 
identification of the domains of Nox1 and betaPix responsible for the 
interaction between the two proteins. GST pull-down assays show that the PH 
domain of betaPix binds to the FAD-binding region of Nox1. We also show that 
overexpression of the PH domain of betaPix results in inhibition of superoxide 
anion generation in response to EGF. Additionally, NADPH oxidase Organizer 1 
(NoxO1) is shown to interact with the NADPH-binding region of Nox1. These 
results suggest that the formation of the complex consisting of Nox1, betaPix, 
and NoxO1 is likely to be a critical step in EGF-induced ROS generation.