Partial purification and characterization of cytosolic Tyr-protein kinase(s) from human erythrocytes.
Tyrosine-protein kinase, phosphorylating tyrosine residues of transmembrane band 3 protein, has been partially purified from human erythrocyte cytosol by DEAE-Sepharose chromatography followed by heparin-Sepharose chromatography. Such a Tyr-protein kinase (36 kDa), as distinct from the Ser/Thre-protein kinases (casein kinase S and TS), appears to display a broader site specificity than does the previously described human erythrocyte P-Tyr-protein phosphatase, dephosphorylating band 3 protein. That is, it is able to phosphorylate not only the highly acidic copolymer poly(Glu-Tyr) but also angiotensin II, lacking an acidic amino acid sequence around the target Tyr residue. Moreover, the phosphorylation of these two substrates exhibits a different pH dependence and a different response to NaCl and 2,3-bisphosphoglycerate. These results suggest that in intact erythrocytes the cytosolic Tyr-protein kinase might phosphorylate band 3 not only on Tyr-8, surrounded by several acidic side-chains (as demonstrated preferentially to occur in isolated ghosts), but also on other Tyr residues surrounded by other amino acid sequences.
Clari
G
G
Istituto di Chimica Biologica dell'Università di Verona, Italy.
Brunati
A M
AM
Moret
V
V
D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology*; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000302:isolation & purification; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000097:blood / Q000302:isolation & purification*
D001457:Anion Exchange Protein 1, Erythrocyte; D008565:Membrane Proteins; D011505:Protein-Tyrosine Kinases