NADPH oxidase (Nox) family enzymes are one of the main sources of cellular 
reactive oxygen species (ROS), which have been implicated in several 
physiological and pathophysiological processes. To date seven members of this 
family have been reported, including Nox1-5 and Duox1 and 2. With the exception 
of Nox2, the regulation of the Nox enzymes is still poorly understood. Nox1 is 
highly expressed in the colon, and requires two cytosolic regulators, the 
organizer subunit NoxO1 and the activator subunit NoxA1, as well as the binding 
of Rac1 GTPase, for its activity. Recently, we identified the c-Src substrate 
proteins Tks4 and Tks5 as functional members of a p47(phox)-related organizer 
superfamily. As a functional consequence of this interaction, Nox1 localizes to 
invadopodia, actin-rich membrane protrusions of cancer cells which facilitate 
pericellular proteolysis and invasive behavior. Here, we report that Tks4 and 
Tks5 directly bind to NoxA1. Moreover, the integrity of the N-terminal PRR of 
NoxA1 is essential for this direct interaction with the Tks proteins. When the 
PRR in NoxA1 is disrupted, Tks proteins cannot bind NoxA1 and lose their ability 
to support Nox1-dependent ROS generation. Consistent with this, Tks4 and Tks5 
are unable to act as organizers for Nox2 because of their inability to interact 
with p67(phox), which lacks the N-terminal PRR, thus conferring a unique 
specificity to Tks4 and 5. Taken together, these results clarify the molecular 
basis for the interaction between NoxA1 and the Tks proteins and may provide new 
insights into the pharmacological design of a more effective anti-metastatic 
strategy.