Topology of Anion Carrier and Acetylcholine Receptor

利用蛋白质化学和免疫化学技术研究动物细胞质膜中乙酰胆碱受体和阴离子载体两种蛋白质的拓扑结构和功能上的重要构象变化。密封的右向外的囊泡或完整的细胞将被用来确定在质膜的哪一侧有特定的氨基酸，与囊泡或细胞无关的试剂将通过免疫吸附剂分离含有修饰氨基酸的肽来建立。中性或带电的亲电试剂对阴离子载体中特定氨基酸的修饰速率的变化将随后通过免疫吸附分离修饰肽。这些结果将暗示该蛋白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蛋白质的高分辨率结构相关。在红细胞阴离子载体催化的偶联阴离子运输过程中，蛋白质的拓扑结构和构象变化都与其催化机制有关。除了在结构上很有趣，这两种蛋白质在几个生理过程中也很重要。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。阴离子载体负责碳酸氢盐通过红细胞的质膜运输，从而使碳酸氢盐从外周组织有效地转移到肺部。细胞质膜是一个包住活细胞质的薄袋。这个包保护细胞质免受细胞外部发生的意外变化，就像我们的皮肤包含和保护我们一样。化学物质通过质膜的过程受到严格控制。这种控制是由嵌入在质膜中的蛋白质来执行的。这些蛋白质中的每一种都像一个看门人一样打开和关闭，以允许特定的分子在特定的时间通过膜。我们正在研究一种蛋白质，它是钠离子和钾离子的把关者，也是氯离子和碳酸氢盐离子的把关者。第一种蛋白质位于肌肉细胞上，直到神经细胞和钾流出，导致肌肉细胞收缩，它才会关闭。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，在那里它变成了二氧化碳。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. ***