Protein kinase activities and membrane autophosphorylation reactions of normal and abnormal human erythrocytes were analyzed. Erythrocytes from patients with high
reticulocytosis due to
sickle cell anemia and other disorders (n = 13) exhibited elevated activities of total and membrane-bound cAMP-independent
casein kinase and cAMP-stimulated
histone kinase. Relative to normal controls (n = 10), the average total activities in these abnormal cells were increased 50% and 81%, respectively. The
casein and
histone kinase activities of normal and abnormal erythrocytes declined significantly with increasing age and buoyant density in Stractan density gradients.
Casein kinase activity was highly correlated (r = 0.88; n = 23) with the percentage of reticulocytes in the fraction, consistent with either a progressive loss of activity in mature erythrocytes or an abrupt decline during reticulocyte maturation. The cAMP-independent and cAMP-stimulated autophosphorylation activities of isolated membranes also declined with increasing erythrocyte age. On average, the initial rate of
spectrin labeling was 36% lower in ghosts from Stractan gradient bottom fractions, relative to ghosts from top fractions similarly incubated with gamma-32P-ATP. Incorporation into the "band 4.5 zone" (primarily labeling bands 4.8 and 4.9, mol wt 47,800 and 44,600) was also age-dependent. In membranes of unfractionated sickle cells,
spectrin autophosphorylation was within normal limits, while 4.5 zone autophosphorylation was increased. Membranes from high
reticulocytosis controls (
vitamin B-12 deficiency) exhibited similar autophosphorylation patterns, suggesting that the altered autophosphorylation pattern of sickle cell membranes may be attributed to the predominance of very young cells.