MECHANISM OF THE CA/H EXCHANGE PUMP

这项研究的长期目标是阐明一些 离子转运的机制，以确定细胞质的变化， Mileau调节离子转运，并确定细胞内 环境改变运输速率。 该项目的重点是 钙调素激活红细胞的钙泵，这是血浆的模型 其他细胞的膜钙泵。 最近的证据表明， 泵介导Ca/H交换，也介导Ca运输而无H移动。 钙泵的当前型号。同时包括ATP，ADP， 磷酸盐和Ca不明确考虑质子。 这项资助的具体目的是研究细胞外 质子和ATP对红细胞钙泵的影响。 有些问题 审查的是： 1. 质子对于Ca ~（2+）离子注入后重新设置泵机制是否重要 半周期？ 2. 必须在ATP绑定之前绑定Ho才能加速返回 在下一个泵循环之前，运输站点可以发生什么？ 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对几种细胞的影响。 钙泵的部分反应，包括Ca/Ca交换、泵逆转 和磷中间体分解。 动力学研究的目标之一 是确定哪些构象变化是由膜的改变引起的 环境会调节泵的活动。 在红细胞中， 为了确定细胞内质子，钙离子， 核苷酸浓度和细胞外质子和钙离子。 这一点很重要，因为，例如，Cai和Ho是底物，但Cao和Hi是底物。 正向泵循环的产物。 钙的瞬时升高很重要 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。 缺陷 钙泵活性将导致钙增加，随后增加 在Na和K中。 这些变化将改变关键的细胞质功能。 等 离子改变与几种疾病状态有关， 肾和心脏衰竭、高血压和肌肉萎缩症。 镰状细胞中红细胞钙泵的改变已被报道 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.