Plasma membrane-associated phosphatase activities hydrolyzing [32P]phosphotyrosyl histones and [32P]phosphatidylinositol phosphate |
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Authors: | S S Imes N O Kaplan A F Knowles |
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Institution: | 1. Department of Mathematics, VNIT, Nagpur, Maharashtra 440010, India;2. Department of Mathematics, Amrita Vishwa Vidyapeetham, Deemed to be University, Coimbatore 641112, India |
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Abstract: | We describe a procedure of preparing 32P]phosphotyrosyl histones with minimal contamination by 32P-labeled lipids; the latter was usually found to be mixed with the phosphoproteins when the cell membrane-enriched fraction of A-431 cells was used as a source of tyrosine kinase. The phosphatase activities previously found to be associated with the plasma membranes of a human astrocytoma were resolved using purified 32P]phosphotyrosyl histones and 32P]phosphatidylinositol phosphate. In comparison with the phosphotyrosyl protein phosphatase, the phosphatidylinositol phosphate phosphatase activity is more active over a broad range of pH values, and its activity is inhibited by fluoride, zinc chloride, and lower concentrations of vanadate. |
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