Calcium regulation of magnesium dependent phosphorylation of human erythrocyte ghost spectrin.
Phosphorylation of human erythrocyte ghost membrane proteins was found to be affected by micromolar calcium concentrations. Increasing Ca2+ concentration to 0.2 microM decreased spectrin (band 2) phosphorylation to 30 +/- 6% of control (to which no calcium was added). Decreasing calcium concentration by adding EGTA (0.2mM) to the standard membrane preparation increased spectrin phosphorylation to 575% control. This effect of Ca2+ was more pronounced at higher temperature. At 0 degree C, Ca2+ (0.05mM) had no effect on protein phosphorylation. Sodium fluoride like EGTA caused a four to five fold increase in phosphorylation. Pyrophosphate, a phosphoprotein phosphatase inhibator, had no effect. Once spectrin was phosphorylated in the presence of [gamma-32P]ATP the addition of Ca2+ or EGTA did not decrease or increase its phosphorylation. It is suggested that calcium regulates spectrin phosphorylation either by decreasing kinase activity or by decreasing substrate availability.
D002118:Calcium / Q000097:blood; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D006801:Humans; D008274:Magnesium / Q000097:blood; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood*; D013049:Spectrin / Q000378:metabolism*; D013696:Temperature
D013049:Spectrin; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D008274:Magnesium; D005459:Fluorides; D002118:Calcium