Mielke D L, Wallace B A
Department of Chemistry Rensselaer Polytechnic Institute, Troy, New York 12181.
J Biol Chem. 1988 Mar 5;263(7):3177-82.
Circular dichroism (CD) spectroscopy was used to determine that the secondary structure of purified nicotinic acetylcholine receptor (AChR) of Torpedo californica in both reconstituted vesicles and a cholate-solubilized state is, on average, 23% alpha-helix, 43% beta-sheet, 6% beta-turn, and 28% random coil. These data can serve to test models by placing limits on the particular types of secondary structural motifs which make up the receptor. A number of models proposed for the AChR are discussed in relation to the experimental data presented. Additionally, the protein in both vesicle and solubilized environments was exposed to an agonist, carbamylcholine, or a competitive antagonist, hexamethonium, to monitor net conformational changes upon ligand binding. The protein secondary structure was not changed upon solubilization, nor was any large net conformational change observed upon ligand binding, although small local or compensatory changes cannot be ruled out.
圆二色（CD）光谱法被用于确定加州电鳐纯化的烟碱型乙酰胆碱受体（AChR）在重构囊泡和胆酸盐溶解状态下的二级结构，平均而言，其α-螺旋为23%，β-折叠为43%，β-转角为6%，无规卷曲为28%。这些数据可通过对构成受体的特定类型二级结构基序设置限制来检验模型。结合所呈现的实验数据，讨论了针对AChR提出的多种模型。此外，将囊泡和溶解环境中的蛋白质分别暴露于激动剂氨甲酰胆碱或竞争性拮抗剂六甲铵，以监测配体结合时的净构象变化。溶解后蛋白质二级结构未发生变化，配体结合时也未观察到任何大的净构象变化，不过不能排除存在小的局部或补偿性变化。
