The members of the NOX family of enzymes are expressed in a variety of tissues 
and serve a number of functions. There is a high level of conservation of 
primary protein sequence, as well as functional features, although specialized 
responses are beginning to emerge. In this context, our data demonstrate that 
the NOX1 cytoplasmic domains interact efficiently with the cytoplasmic subunits 
of the phagocyte NADPH oxidase and identify the second cytoplasmic loop of NOX 
electron transporters as a crucial domain for enzyme function. Studies of 
cytosolic co-factors showed that the C-terminal cytoplasmic domain of NOX1 was 
absolutely required for activation with NOXO1 and NOXA1 and that this activity 
required interaction of the putative NADPH-binding region of this domain with 
NOXA1. Finally, we have provided the first example of how alternative splicing 
of a NOX co-factor may be involved in the regulation of NADPH oxidase function.