Phox homology domains specifically bind phosphatidylinositol phosphates.
The recruitment of specific cytosolic proteins to intracellular membranes through binding phosphorylated derivatives of phosphatidylinositol (PtdIns) controls such processes as endocytosis, regulated exocytosis, cytoskeletal organization, and cell signaling. Protein modules such as FVYE domains and PH domains that bind specifically to PtdIns 3-phosphate (PtdIns-3-P) and polyphosphoinositides, respectively, can direct such membrane targeting. Here we show that two representative Phox homology (PX) domains selectively bind to specific phosphatidylinositol phosphates. The PX domain of Vam7p selectively binds PtdIns-3-P, while the PX domain of the CPK PI-3 kinase selectively binds PtdIns-4,5-P(2). In contrast, the PX domain of Vps5p displays no binding to any PtdInsPs that were tested. In addition, the double mutant (Y42A/L48Q) of the PX domain of Vam7p, reported to cause vacuolar trafficking defects in yeast, has a dramatically decreased level of binding to PtdIns-3-P. These data reveal that the membrane targeting function of the Vam7p PX domain is based on its ability to associate with PtdIns-3-P, analogous to the function of FYVE domains.
Song
X
X
Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, Massachusetts 01605, USA.
Xu
W
W
Zhang
A
A
Huang
G
G
Liang
X
X
Virbasius
J V
JV
Czech
M P
MP
Zhou
G W
GW
D020816:Amino Acid Motifs; D002352:Carrier Proteins / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D008081:Liposomes; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; C494208:SNAP25 protein, human; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; C106932:VPS5 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C055525:phosphatidylinositol 3-phosphate; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases