The PX domain as a novel phosphoinositide- binding module.
The phox (phagocyte oxidase) homology (PX) domain occurs in the mammalian phox proteins p40(phox) and p47(phox), the polarity establishment protein Bem1p in budding yeast, and a variety of proteins involved in membrane trafficking. Here we show that the PX domains of p40(phox) and p47(phox) directly bind to phosphoinositides: p40(phox) prefers Ptdlns(3)P, while p47(phox) does Ptdlns(4)P and Ptdlns(3,4)P(2). In addition, the Bem1p PX domain also interacts with Ptdlns(4)P. When the p40(phox) PX domain is expressed as a fusion to green fluorescent protein in HeLa cells, it exists at early endosomes where Ptdlns(3)P is enriched. Furthermore, a mutant p40(phox) PX carrying the substitution of Lys for Arg105 only weakly binds to phosphoinositides in vitro, and fails to locate to early endosomes. Thus the PX domain functions as a novel phosphoinositide-binding module and likely participates in targeting of proteins to membranes.
Ago
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Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Takeya
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Hiroaki
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Kuribayashi
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Ito
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Kohda
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Sumimoto
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H
D000595:Amino Acid Sequence; D004305:Dose-Response Relationship, Drug; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D019255:NADPH Oxidases; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D008164:Luminescent Proteins; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C085072:neutrophil cytosol factor 40K; C055525:phosphatidylinositol 3-phosphate; C037178:phosphatidylinositol 4-phosphate; D049452:Green Fluorescent Proteins; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D010744:Phosphoric Monoester Hydrolases; C053153:phosphatidylinositol-3,4-bisphosphate 4-phosphatase