| Abstract: | Membrane protein phosphorylation by protein kinases in normal red cells takes place mainly on band 2 at the basal activity, and on bands 1 and 2.1 in the presence of cyclic 3':5'-adenosine monophosphate. Calcium precipitates preferentially bands 1 and 2.1 on extracted membrane proteins, and inhibit the membrane protein phosphorylation. Phosphorylation of endogeneous membrane proteins is diminished in red cells of some patients with hereditary spherocytosis (HS), partly corresponding reciprocally to MCHC, % spherocytes and reticulocytosis in peripheral blood of these patients, although the enzymatic activities of glyceraldehyde-3-phosphate dehydrogenase as a marker of the inner surface of red cell membranes are maintained normally in these red cells. The pattern of membrane protein fractions in HS red cells as endogeneous substrates for phosphorylation reactions is almost identical to that in normal red cells. Activities to phosphorylate casein or histone as exogeneous substrates are normal in HS red cell ghosts. |
