Ca2(+)-dependent membrane-binding proteins in normal erythrocytes and erythrocytes from patients with chronic...

Cytosolic and membrane fractions of human erythrocytes were probed with antisera raised against several members of the annexin family of Ca2(+)-dependent phospholipid/membrane-binding proteins. One of the antisera, that against the 67 Kd calcimedin, identified erythrocyte polypeptides of molecular weights 48 and 67 Kd, which were found in the cytoplasm when normal erythrocytes were lysed in the presence of EGTA but on the membrane when lysis buffers contained Ca2+. In contrast, membranes of erythrocytes from patients with chronic myelogenous leukemia (CML) contained the 67 Kd protein even when prepared in the absence of Ca2+, as well as the antibody-reactive proteins of 35 and 38 Kd. When prepared in the presence of Ca2+, CML membranes contained increased levels of these three species and the 48 Kd protein, as well. These results suggest that normal erythrocytes contain a calcimedin-like protein that is translocated to the membrane in the presence of Ca2+ and that CML erythrocytes have both an abnormal amount and distribution of calcimedin-like proteins.