MECHANISM OF THE CA/H EXCHANGE PUMP

这项研究的长期目标是阐明一些 离子转运机制，以确定胞质如何变化 Mileau调制离子运输，并确定细胞内 环境改变了运输速度。这个项目的重点是 钙调素激活的红细胞钙泵是一种血浆模型 其他细胞的膜钙泵。最近的证据表明，这种情况 泵参与了钙/氢交换和钙的运输，而不需要氢的移动。 当前型号的钙泵。同时还包括ATP、ADP、 磷酸盐和钙不明确地考虑质子。 这项拨款的具体目的是检查细胞外的影响 红细胞钙泵上的质子和三磷酸腺苷。要回答的一些问题是 检查的内容包括： 1.情况发生后，质子对于重新设置泵机构是否重要 半周期的吗？ 2.在ATP可以结合之前，必须先进行HO绑定，以加速 运输地点在下一个泵周期之前可以发生吗？ 3.当质子不被传输时，传输的是什么？ 实验方案是检查ATP和H对几个 钙泵的部分反应，包括钙/钙交换、泵反转 和磷中间分解。动力学研究的目标之一 就是确定通过膜的改变而发生的构象变化 环境会调节泵的活动。在红血球中，这是可能的 为了确定细胞内质子、钙离子、 核苷酸浓度，以及胞外质子和钙离子。 这很重要，因为例如，Cai和Ho是底物，而CaO和Hi是底物 前向泵循环的产品。钙的短暂上升是很重要的 用于在心脏、骨骼肌和平滑肌等过程中发出信号 收缩、细胞分化和终止信号。中的缺陷 钙泵的活性会导致钙的增加，随后会增加 在Na和K中，这些变化会改变关键的细胞质功能。是这样的 离子变化与几种疾病状态有关，包括 肾功能衰竭、心力衰竭、高血压和肌肉营养不良。 据报道，镰状细胞中的红细胞钙泵发生了变化 疾病。

The long-term objectives of this research are to elucidate some of the mechanisms of ion transport, to determine how changes of the cytosolic mileau modulate ion transport, and to determine how changes of the cellular environment alter transport rate. The focus of this project is the calmodulin activated Ca pump of red cells, which is a model for plasma membrane Ca pumps in other cells. Recent evidence indicates that the Ca pump mediates Ca/H exchange and also Ca transport without H movement. Current models of the Ca pump. while including roles for ATP, ADP, phosphate, and Ca, do not explicitly consider protons. The specific aims of this grant are to examine the effects of extracellular protons and ATP on the red cell Ca pump. Some of the questions to be examined are: 1. Are protons important for resetting the pump mechanism after the Ca half cycle? 2. Must Ho bind before ATP can bind to accelerate the return of the transport sites before the next pump cycle can occur? 3. When protons are not transported, what is transported instead? The experimental protocol is to examine the effect of ATP and H on several partial reactions of the Ca pump, including Ca/Ca exchange, pump reversal and phosphointermediate decomposition. One of the goals of a kinetic study is to determine which conformational changes by alterations in the membrane environment would modulate pump activity. In the red cell it is possible to determine the separate effects of intracellular protons, calcium ions, nucleotide concentrations, and extracellular protons and calcium ions. This is important since, e.g., Cai and Ho are substrates but Cao and Hi are products of the forward pump cycle. A transient rise in Ca is important for signalling in such processes as cardiac, skeletal, and smooth muscle contraction, cell differentiation and terminating the signal. Defects in Ca pump activity would lead to an increase in Ca with subsequent increases in Na and K. These changes would alter key cytoplasmic functions. Such ionic alterations have been implicated in several disease states including renal and cardiac failure, hypertension, and muscular dystrophy. Alterations of the red cell Ca pump have been reported in sickle cell disease.