Binding of the PX domain of p47(phox) to phosphatidylinositol 3,4-bisphosphate and phosphatidic acid is masked by an intramolecular interaction.
p47(phox) is a key cytosolic subunit required for activation of phagocyte NADPH oxidase. The X-ray structure of the p47(phox) PX domain revealed two distinct basic pockets on the membrane-binding surface, each occupied by a sulfate. These two pockets have different specificities: one preferentially binds phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P(2)] and is analogous to the phophatidylinositol 3-phosphate (PtdIns3P)-binding pocket of p40(phox), while the other binds anionic phospholipids such as phosphatidic acid (PtdOH) or phosphatidylserine. The preference of this second site for PtdOH may be related to previously observed activation of NADPH oxidase by PtdOH. Simultaneous occupancy of the two phospholipid-binding pockets radically increases membrane affinity. Strikingly, measurements for full-length p47(phox) show that membrane interaction by the PX domain is masked by an intramolecular association with the C-terminal SH3 domain (C-SH3). Either a site-specific mutation in C-SH3 (W263R) or a mimic of the phosphorylated form of p47(phox) [Ser(303, 304, 328, 359, 370)Glu] cause a transition from a closed to an open conformation that binds membranes with a greater affinity than the isolated PX domain.
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D003001:Cloning, Molecular; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019255:NADPH Oxidases / Q000737:chemistry / Q000378:metabolism; D010712:Phosphatidic Acids / Q000737:chemistry / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000737:chemistry* / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D010712:Phosphatidic Acids; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D021122:Protein Subunits; D011994:Recombinant Proteins; C060980:phosphatidylinositol 3,4-diphosphate; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1