Phosphotyrosine phosphatase associated with band 3 protein in the human erythrocyte membrane.
The anion-exchange band 3 protein is the main erythrocyte protein that is phosphorylated by tyrosine kinase. To study the regulation of band 3 phosphorylation, we examined phosphotyrisine phosphatase (PTP) activity in the human erythrocyte. We show that the human erythrocyte membrane contains a band 3-associated neutral PTP which is activated by Mg2+ and inhibited by Mn2+ and vanadate. The PTP is active in the intact cell and in the isolated membrane. A major fraction of the PTP is tightly bound to the membrane and can be extracted from it by Triton X-100; a minor part is associated with Triton X-100-insoluble cytoskeleton. The behaviour of the PTP parallels that of band 3, the major fraction of which is extractable by detergents with a minor fraction being anchored to the cytoskeleton. Moreover, band 3 is co-precipitated when the PTP is immunoprecipitated from solubilized membranes, and PTP is co-precipitated when band 3 is immunoprecipitated. The PTP appears to be related to PTP1B (identified using an antibody to an epitope in its catalytic domain and by molecular mass). The system described here has a unique advantage for PTP research, since it allows the study of the interaction of a PTP with an endogenous physiological substrate that is present in substantial amounts in the cell membrane. The membrane-bound, band 3-associated, PTP may play a role in band 3 function in the erythrocyte and in other cells which have proteins analogous to band 3.
Zipser
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Y
Department of Human Genetics, Sackler School of Medicine, Tel-Aviv University, Israel.
Kosower
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NS
D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000201:enzymology*; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D008970:Molecular Weight; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis*; D017027:Protein Tyrosine Phosphatases / Q000097:blood* / Q000302:isolation & purification; D013379:Substrate Specificity
D001457:Anion Exchange Protein 1, Erythrocyte; D019000:Phosphotyrosine; D017027:Protein Tyrosine Phosphatases