Properties of Calcium Pumping ATPase

描述(申请人提供)：质膜钙离子泵ATPase特性的研究将继续进行。这些钙离子泵存在于心脏、平滑肌、肾脏、脑、肠上皮、红细胞等多种细胞的质膜中。它们参与控制各种细胞内的游离钙水平，并参与钙离子在细胞层之间的移动，如肠和肾小管上皮细胞。因此，有关这些泵的调节的信息可能会提供与高血压和肾脏疾病等疾病相关的信息。 该泵由一个分子量为127,000-137,000的多肽链组成(确切的分子量取决于异构体)。四个基因编码不同的异构体，其他形式通过交替拼接产生。我们已经成功地在COS和昆虫细胞中表达了这个泵，并建立了检测系统来确定表达的酶的活性，它与钙调蛋白和钙离子的结合。我们提出的研究旨在扩大我们对该酶不同亚型的功能以及钙调蛋白结合残基和钙离子结合残基的了解。我们将测量硝基苯基磷酸酶的活性、泵的激活率和钙调蛋白的结合率。还将进行测量，以观察泵对其先前的钙离子暴露历史的记忆。这些测量将在适当改变的泵形式和不同的异构体上进行。

DESCRIPTION (provided by applicant): Studies on the properties of the calcium ion pumping ATPase of plasma membranes will be continued. These calcium ion pumps exist in the plasma membranes of heart, smooth muscle, kidney, brain, intestinal epithelium, erythrocyte and many other cell types. They are involved in control of intracellular free calcium levels in cells of all kinds, and in movement of calcium ions across cell layers such as the intestinal and kidney tubule epithelia. Information about the regulation of these pumps may thus give information relevant to hypertension and kidney disease, among other conditions. The pump consists of a single polypeptide chain of molecular weight 127,000-137,000 (the exact molecular weight depends on the isoform). Four genes encode different isoforms, and additional forms are created by alternate splices. We have succeeded in expressing this pump in COS and insect cells and have developed assay systems for determining the activity of the expressed enzyme, its binding of calmodulin and of calcium ions. We propose studies designed to extend our knowledge of the function of the different isoforms of this enzyme, and of the calmodulin-binding and calcium ion-binding residues. We will make measurements of the nitrophenyl phosphatase activity, of the rates of the activation of the pump and of the binding of calmodulin. Measurements will also be made to observe the memory of the pump for its previous history of calcium ion exposure. These measurements will be made on appropriately altered forms of the pump and on the different isoforms.