Abstract
In human erythrocytes Ser/Thr- and Tyr-phosphorylations of cytoplasmic domain of band 3 are catalyzed by casein kinase I and Tyr-protein kinase respectively, both distributed between cytosol and membrane structures. The results reported here show that purified cytosolic Tyr-protein kinase activity, assayed on added substrates such as poly(Glu,Tyr)4:1 and isolated chymotryptic fragments of band 3 cytoplasmic domain (cdb3), is potently inhibited by PIP and even more by PIP2. Similar inhibitory effects are displayed by these polyphosphoinositides also on the endogenous Tyr-phosphorylation of band 3, when they are added to the isolated native membranes, thus suggesting their involvement in regulating in-vivo Tyr-phosphorylation of membrane proteins.
MeSH terms
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Adenosine Triphosphate / metabolism
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Anion Exchange Protein 1, Erythrocyte / metabolism
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Chymotrypsin / metabolism
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Erythrocytes / enzymology*
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Humans
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Hydrogen-Ion Concentration
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Peptide Fragments / blood
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Phosphatidylinositol 4,5-Diphosphate
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Phosphatidylinositol Phosphates*
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Phosphatidylinositols / pharmacology*
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Phosphoserine / metabolism
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Phosphotyrosine
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Protein-Tyrosine Kinases / antagonists & inhibitors*
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Protein-Tyrosine Kinases / blood
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Tyrosine / analogs & derivatives
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Tyrosine / blood
Substances
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Anion Exchange Protein 1, Erythrocyte
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Peptide Fragments
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Phosphatidylinositol 4,5-Diphosphate
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Phosphatidylinositol Phosphates
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Phosphatidylinositols
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phosphatidylinositol 4-phosphate
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Phosphoserine
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Phosphotyrosine
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Tyrosine
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Adenosine Triphosphate
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Protein-Tyrosine Kinases
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Chymotrypsin