This entry represents the polybasic or autoinhibitory region (PBR/AIR, an arginine/lysine rich region) found after the second SH3 domain in neutrophil cytosol factor 1 (NCF1 or p47phox) [1]. NCF1 is one of the cytosolic regulatory components of NADPH oxidase and consists of a PX domain at the N-terminal (Pfam:PF00787), two tandem SH3 domains (Pfam:PF00018), a PBR/AIR and a proline-rich region at the C-terminal (Pfam:PF08944). In the resting state, the SH3 domains of NCF1 are masked by an intramolecular interaction with the PBR/AIR, which maintains the enzyme in an inactive form [2].

1: Molecular basis of phosphorylation-induced activation of the NADPH oxidase. Groemping Y, Lapouge K, Smerdon SJ, Rittinger K; Cell. 2003;113:343-355. PMID:12732142

2: NMR solution structure of the tandem Src homology 3 domains of p47phox complexed with a p22phox-derived proline-rich peptide. Ogura K, Nobuhisa I, Yuzawa S, Takeya R, Torikai S, Saikawa K, Sumimoto H, Inagaki F; J Biol Chem. 2006;281:3660-3668. PMID:16326715