Membrane protein phosphorylation in intact normal and sickle cell erythrocytes

Membrane protein phosphorylation was measured in intact normal and sickle erythrocytes, by determining the incorporation of 32Pi. The general pattern of radiolabeling is similar for normal and sickle cells, but sickle erythrocytes incorporate approximately twice as much 32P as normal cells, and the detailed distribution of label is altered. Sickle cells incorporate less of their 32P into spectrin band 2 and more into band 4.5 than do normal cells. Although irreversibly sickled cells do not incorporate more 32P than the general sickle cell population, the distribution of label among their membrane polypeptides is more abnormal. These differences between normal and sickle cells are seen throughout an 18-h incubation. All polypeptides become labeled at approximately the same rat. The differences in phosphorylation between sickle and normal cells cannot be attributed to relative cell age, ATP levels, or the rate of 32P labeling of the ATP pool. It appears that altered membrane phosphorylation is an intrinsic characteristic of sickle cell anemia.