Tyrosine phosphorylation of cytosolic proteins in human erythrocytes

Some cytosolic proteins of human erythrocytes can be phosphorylated on tyrosine residues by endogenous Tyr-protein kinase(s). Their phosphorylation is enhanced by addition of Tyr-protein kinase, purified from human erythrocyte cytosol. The most phosphorylatable is a 19 kDa protein. Its phosphorylation is more activated by Mn2+ than by Mg2+. It is inhibited by NaC1, 2,3-bisphosphoglycerate and by heparin. Similar response to the above effectors is exhibited by the phosphorylation of the other protein bands. However, the phosphorylation of a 73 kDa double band, which is negligible in the absence of added NaC1, is stimulated by this salt.