Oxidative lesion to membrane proteins in senescent erythrocytes

The oxidative lesion undergone by membrane proteins in senescent human erythrocytes was evaluated by assaying their MetSO and thiol group content in ghosts and the amount of a coumarinyl derivative of maleimide, the DACM, bound by individual membrane proteins after treatment of erythrocytes of different age with this reagent. Quantitation of MetSO content of ghost membranes indicates an increase of the oxidative state of membrane proteins from young to mature and senescent erythrocytes, while thiol group assay does not show significant differences among erythrocytes of different age. Quantitation of DACM bound in intact cells by individual membrane proteins shows a decreased accessibility of thiol groups of band 3 protein and of the main proteins of the membrane skeleton in senescent erythrocytes, and this could be partly due to oxidation. The decreased reactivity to DACM of senescent erythrocyte band 3 seems to concern thiols located on the cytoplasmic domain of this protein, since the anion channel binds the same amount of the anion transport inhibitor EM, in mature and senescent erythrocytes.