PHOSPHORYLATION OF HUMAN ERYTHROCYTE BAND-3 BY ENDOGENOUS P72(SYK)

The anion transporter, band 3, is the major tyrosine kinase substrate in both red cell membranes and intact human erythrocytes. Using antibo dies to various protein-tyrosine kinases, we found that p72syk and p56 /53lyn are present in human red cells, while p56lck, pp60src, p59fyn, and p55blk are absent. Treatment of intact red cells with a combinatio n of vanadate and hydrogen peroxide dramatically increased the tyrosin e phosphorylation of band 3. This treatment increased the tyrosine kin ase activity of p72syk and decreased the activity of p56/53lyn in immu ne complex kinase assays. Band 3 was found to be associated in immune complexes with p72syk but not with p56/53lyn. These findings suggest t hat p72syk is responsible, at least in part, for the tyrosine phosphor ylation of band 3 in human erythrocytes.