Signaling inositol polyphosphate-5-phosphatase. Characterization of activity and effect of GRB2 association.

Division of Hematology-Oncology, Washington University School of Medicine, Box 8125, St. Louis, Missouri 63110, USA.
An inositol polyphosphate-5-phosphatase (SIP-110) that binds the SH3 domains of the adaptor protein GRB2 was produced in Sf9 cells and characterized. SIP-110 binds to GRB2 in vitro with a stoichiometry of 1 mol of GRB2/0.7 mol of SIP-110. GRB2 binding does not affect enzyme activity implying that GRB2 serves mainly to localize SIP-110 within cells. SIP-110 hydrolyses inositol (Ins)(1,3,4,5)P4 to Ins(1, 3,4)P3. The enzyme does not hydrolyze Ins(1,4,5)P3 that is a substrate for previously described 5-phosphatases nor does it hydrolyze phosphatidylinositol (PtdIns)(4,5)P2. SIP-110 also hydrolyzed PtdIns(3,4,5)P3 to PtdIns(3,4)P2 as did recombinant forms of two other 5-phosphatases designated as inositol polyphosphate-5- phosphatase II, and OCRL (the protein that is mutated in oculocerebrorenal syndrome). The inositol polyphosphate-5-phosphatase enzyme family now is represented by at least 9 distinct genes and includes enzymes that fall into 4 subfamilies based on their activities toward various 5-phosphatase substrates.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Animals, Chromatography, High Pressure Liquid, GRB2 Adaptor Protein, Hot Temperature, Hydrolysis, Kinetics, Phosphoric Monoester Hydrolases, Proteins, Receptor, Epidermal Growth Factor, Spodoptera, Substrate Specificity
J. Biol. Chem. Feb. 28, 1997; 272(9);5983-8 [PUBMED:9038219]
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