TOPOLOGY AND MECHANISMS BY SITE-DIRECTED IMMUNOCHEMISTRY

描述：特定氨基酸的共价修饰， 选定的蛋白质被用来检查结构和机制 问题. 跨越双层的三种蛋白质的结构， 通过动物细胞的质膜运输离子，阴离子 Na/K-ATP酶和乙酰胆碱受体，正在被探索， 具有不渗透化学试剂的密封系统， 在它们的表面上有特殊类型的氨基酸。 通过分配 将天然蛋白质中的特定氨基酸转移到其细胞质表面 或其细胞质外表面，氨基的疏水片段 每种蛋白质的酸性序列，形成沿着的途径， 可以识别跨膜传输的离子。 半胱氨酸 在核糖核苷酸还原酶的活性位点内， 正在接受检查。 有人提出在化学反应过程中 在这种酶的催化下，这些半胱氨酸要么变成自由基， 或彼此联合收割机形成胱氨酸。 的利率和 这些转变发生的顺序正在审查， 将酶与核糖核苷酸快速混合， 反应时间短。 在所有这些实验中， 通过使用抗体从消化的蛋白质中分离出来， 识别这些肽中氨基酸的特征序列。 这些抗体能够挑选出所需的肽 含有来自以下物质的复杂混合物的感兴趣的氨基酸 由这些大蛋白质中的每一种消化产生的肽。 以这种方式，实现了有效和快速的纯化。 每一种被研究的蛋白质都负责一个重要的 生物功能。 阴离子交换器负责运输 碳酸氢盐穿过红细胞的质膜， 二氧化碳从外周组织的有效运输 到肺部。 Na/K-ATP酶造成离子浓度的不平衡 穿过细胞的质膜，提供能量， 营养吸收和神经组织的电活动。 乙酰胆碱受体产生电信号， 神经冲动转化为肌肉的收缩。 核糖核苷酸 还原酶产生所有的脱氧核糖核苷酸所需的 DNA的复制和修复。

DESCRIPTION: The covalent modification of particular amino acids in selected proteins is being used to examine structural and mechanistic questions. The structures of three proteins that span the bilayer and transport ions across the plasma membrane of animal cells, anion exchanger, Na/K-ATPase and acetylcholine receptor, are being probed in sealed systems with impermeant chemical reagents that react with particular types of animo acids on their surfaces. By assigning specific amino acids in the native protein to its cytoplasmic surface or its extracytoplasmic surface, the hydrophobic segments of the amino acid sequence of each protein that form the pathways along which the ions are transported across the membrane can be identified. Cysteines within the active site of the enzyme ribonucleotide reductase are also being examined. It has been proposed that during the chemical reaction catalyzed by this enzyme, these cysteines either become free radicals or combine with each other to form cystines. The rates at which and the sequence in which these transformations occur are being examined by rapidly mixing the enzyme with a ribonucleotide and quenching the reaction at short times. In all of these experiments, specific peptides are being isolated from the digested proteins by using antibodies that recognize characteristic sequences of amino acids in these peptides. These antibodies are able to pick out just the desired peptide containing the amino acid of interest from the complex mixture of peptides resulting from the digestion of each of these large proteins. In this way, efficient and rapid purifications are achieved. Each of the proteins being studied is responsible for an important biological function. Anion exchanger is responsible for transport of bicarbonate across the plasma membrane of the erythrocyte that permits the efficient transport of carbon dioxide from the peripheral tissues to the lungs. Na/K-ATPase creates the imbalances in ion concentration across the plasma membrane of the cell that provide the energy for nutrient uptake and the electrical activity of nervous tissue. Acetylcholine receptor creates the electrical signals that transform nerve impulses into the contractions of a muscle. Ribonucleotide reductase produces all of the deoxyribonucleotides needed for the duplication and repair of DNA in the cell.