Pant H C, Virmani M
Physiol Chem Phys Med NMR. 1984;16(4):283-91.
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.
人们发现，微摩尔浓度的钙会影响人红细胞血影膜蛋白的磷酸化。将钙离子浓度增至0.2微摩尔时，血影蛋白（第2条带）的磷酸化水平降至对照（未添加钙）的30±6%。在标准膜制剂中添加乙二醇双乙醚二胺四乙酸（EGTA，0.2毫摩尔）以降低钙浓度，可使血影蛋白磷酸化增加至对照的575%。钙离子的这种作用在较高温度下更为明显。在0℃时，钙离子（0.05毫摩尔）对蛋白质磷酸化无影响。与EGTA一样，氟化钠可使磷酸化增加4至5倍。焦磷酸作为一种磷蛋白磷酸酶抑制剂，没有作用。一旦血影蛋白在[γ-32P]ATP存在的情况下发生磷酸化，添加钙离子或EGTA都不会使其磷酸化水平降低或升高。有人提出，钙可能通过降低激酶活性或降低底物可用性来调节血影蛋白的磷酸化。
