Zinc ions and alkaline PH alter the phosphorylated state of proteins 3 and 4.2 in human erythrocyte membranes

The phosphorylation patterns of isolated red blood cell (RBC) membranes labeled with [ γ-³²p]ATP are altered by Zn⁺⁺ ions. Zn⁺⁺ ions caused an increased phosphate incorporation into a 72 KDa protein and several proteins in the 40–60 KDa region and a decrease in the labeling of a 53 KDa protein. The 72 KDa and 53 KDa proteins have been identified as protein 4.2 and a protease-cleaved fragment of protein 3, respectively. Evidence suggests that the changes in phosphorylation pattern may be due to the stimulation of endogenous membrane alkaline phosphatase(s). Our results suggest that Zn⁺⁺, at physiological concentrations in the intact erythrocyte, could modulate the phosphorylation of selected proteins which may regulate their association in the cytoskeletal network.