DIDS-effect on Ser/Thr- and Tyr-phosphorylation of membrane proteins in human erythrocytes

Band 3, the major transmembrane multifunctional protein of human erythrocytes, has been found to be phosphorylated-dephosphorylated on both Ser/Thr- and Tyr-residues by specific protein kinases and protein phosphatases. The results reported here would indicate that the ghosts prepared from human erythrocytes pretreated with DIDS, well known inhibitor of band 3-mediated anion transport, exhibit a markedly reduced Ser/Thr-phosphorylation of spectrin and band 3, when incubated with [gamma-32P]ATP in the presence of Mg2+. On the other hand, Tyr-phosphorylation of this latter protein is practically unchanged or even slightly enhanced. This suggests that Ser/Thr- and Tyr-phosphorylation of band 3 display a different functional role.