Topology of Anion Carrier and Acetylcholine Receptor

本论文应用蛋白质化学和免疫化学技术研究了动物细胞质膜上乙酰胆碱受体和阴离子载体两种蛋白质的拓扑结构和重要功能构象的变化。 将使用密封的正面朝外囊泡或完整细胞，通过免疫吸附剂分离含有修饰的氨基酸的肽，确定在质膜的哪一侧上将建立特定的氨基酸，其中试剂对囊泡或细胞不渗透。 通过中性或带电亲电体对阴离子载体中特定氨基酸的修饰速率的变化将通过免疫吸附分离修饰的肽来跟踪。 这些结果将暗示该蛋白质中的特定位置在功能上重要的结构变化。 乙酰胆碱受体的拓扑结构将与最近的高分辨率结构的蛋白质。 红细胞阴离子载体催化偶联阴离子转运过程中蛋白质的拓扑结构和构象变化与其催化机制有关。 除了在结构上有趣之外，这两种蛋白质对几种生理过程至关重要。 乙酰胆碱受体在突触处将神经动作电位转化为肌肉动作电位。 负离子载体负责碳酸氢盐穿过红细胞的质膜的运输，这允许碳酸氢盐从外周组织有效地转移到肺。 细胞质膜是一个薄的袋子，包裹着细胞的活细胞质。 这个袋子保护细胞质免受细胞外部发生的意外变化，就像我们的皮肤容纳和保护我们一样。 化学物质穿过质膜的通道受到严格控制。 这种控制是由包埋在质膜中的蛋白质来执行的。 这些蛋白质中的每一种都充当看门人，打开和关闭以允许特定分子在特定时间通过膜。 我们正在研究一种蛋白质，它是钠离子和钾离子的看门人，还有一种蛋白质是氯离子和碳酸氢根离子的看门人。 第一种蛋白质位于肌肉细胞上，并保持关闭，直到神经细胞和钾流出，这一事件导致肌肉细胞收缩。 第二种蛋白质位于红细胞上，允许细胞在肌肉中吸收碳酸氢盐并将其转移到肺部，在那里变成二氧化碳。 我们正在研究这些蛋白质的设计，使它们能够发挥对肌肉和血液功能至关重要的作用。 ***

Kyte 9406321 The topology and functionally important conformational changes of acetylcholine receptor and anion carrier, two proteins in the plasma membranes of animal cells, will be examined with protein chemical and immunochemical techniques. Sealed right-side-out vesicles or intact cells will be used to determine on which side of the plasma membrane particular amino acids with reagents impermeant to the vesicles or the cells will be established by isolating peptides containing the modified amino acids by immunoadsorbents. Changes in the rate of modification of particular amino acids in anion carrier by neutral or charged electrophiles will be followed by isolating modified peptides by immunoadsorption. These results will implicate particular locations in this protein in functionally important structural changes. The topology of acetylcholine receptor will be correlated with recent high resolution structures of the protein. Both the topology of the protein and the conformational changes involved in the coupled anion transport catalyzed by anion carrier from erythrocytes will be related to the mechanism of its catalysis. In addition to being structurally interesting, these two proteins are of central importance to several physiological processes. Acetylcholine receptor transforms the neural action potential into muscular action potential at the synapse. Anion carrier is responsible for the bicarbonate transport across the plasma membrane of the of the erythrocyte which permits efficient transfer of bicarbonate from peripheral tissue to the lungs. %%% The plasma membrane is a thin bag that encloses the living cytoplasm of a cell. This bag protects the cytoplasm from the unexpected changes that occur on the outside of the cell, much as our skin contains and protects us. The passage of chemicals across the plasma membrane is carefully controlled. This control is enforced by proteins that are embedded in the plasma membrane. Each of these proteins acts as a gatekeeper opening and closing to permit particular molecules to pass through the membrane at specific times. We are studying a protein that is the gatekeeper for sodium and potassium ions and a protein that the gatekeeper for chloride and bicarbonate ions. The first protein is located on muscle cells and remains closed until a nerve cell and potassium to flow out, an event that causes the muscle cell to contract. The second protein is located on red blood cells and allows the cells to pick up bicarbonate in the muscles and transfer it to the lungs where it becomes carbon dioxide. We are studying the design of these proteins that permits them to perform these roles that are essential to the function of muscles and of the blood. ***