The C terminal domain of the phagocyte NADPH oxidase subunit p47Phox contains conserved PxxP motifs that allow binding to SH3 domains, with subsequent activation of the NADPH oxidase, and generation of superoxide, which plays a crucial role in host defence against microbial infection [1].

1: Diverse recognition of non-PxxP peptide ligands by the SH3 domains from p67(phox), Grb2 and Pex13p. Kami K, Takeya R, Sumimoto H, Kohda D; EMBO J 2002;21:4268-4276. PMID:12169629