A CA-DEPENDENT MODULATOR PROTEIN OF THE NA-K ATPASE

作者最近的工作表明，Na-K ATP酶的敏感性 人红细胞钠钾泵对钙的抑制作用增加20 被红细胞胞质中的一种未知蛋白质折叠。 的 蛋白质不是钙调蛋白，似乎与人红细胞膜结合， 细胞的钙依赖性的方式，并增加敏感性的钠钾 在低微摩尔浓度下， 游离钙浓度 如果这种蛋白质也改变了钙对 其他细胞中的Na-K ATP酶，那么它就可以在 在许多情况下，细胞调节钠钾泵。 比如说， 这可能与钠钾泵与 Na/Ca交换和平滑肌中游离Ca的控制， 强心苷变力作用的基础， 钠代谢和高血压之间的联系 拟议项目的第一个目标是纯化和鉴定 蛋白质;二是确定其分子量，氨基酸 组成、末端和可能的辅基。 第三个目标 研究纯化蛋白对Na ~+-K ~+-Ca ~（2+）抑制的影响 第四是建立人红细胞膜ATP酶的分子生物学模型， 对纯化的Na-K ATP酶的影响。 第五个也是最后一个目标是 探讨原发性高血压患者的Na-K ATP酶是否 对钙的抑制作用比正常人更敏感， 纯化的蛋白质可能在这些差异中起作用。 拟议的工作将 需要三年时间才能完成。

Recent work by the author has shown that the sensitivity of the Na-K ATPase and Na-K pump of human red blood cells to inhibition by Ca is increased 20 fold by an unidentified protein present in the cytoplasm of red cells. The protein is not calmodulin, appears to bind to the membrane of human red cells in a Ca-dependent manner, and increases the sensitivity of the Na-K ATPase to the extent that 50% inhibition can occur at low micromolar concentrations of free Ca. If this protein also alters the effect of Ca on the Na-K ATPase in other cells, then it could play a fundamental role in cellular regulation of the Na-K pump under many conditions. For instance, it could be involved in the relationship between the Na-K pump and the Na/Ca exchange and the control of free Ca in smooth muscle which may underlie the inotropic effect of cardiac glycosides and the relationship between sodium metabolism and hypertension. The first aim of the proposed project is to purify and identify the protein; the second is to determine its molecular weight, amino acid composition, end terminals, and possible prosthetic groups. The third aim is to study the effect of the purified protein on Ca inhibition of the Na-K ATPase in human red cell membranes and the fourth is to establish its effect on the purified Na-K ATPase. The fifth and final aim is to investigate if the Na-K ATPase in patients with essential hypertension are more sensitive than normal to inhibition by Ca and to establish what role the purified protein may play in such differences. The proposed work will require three years to complete.