Beck-Sickinger A G, Kiess M, Kern P, Folkers G
Department of Pharmaceutical Chemistry, Swiss Federal Institute of Technology Zürich.
Pharm Acta Helv. 1995 Apr;70(1):33-41. doi: 10.1016/0031-6865(94)00049-2.
The synthesis of 13 segments of porcine adenylate kinase (AK 1) consisting each of 15 residues and covering the whole sequence of AK 1 is reported. The peptides were obtained by multiple peptide synthesis applying Fmoc/tert. butyl strategy. For the conformational analysis by circular dichroism spectroscopy different mixtures of phosphate buffer (pH 7), trifluoroethanol and methanol were used. Ten peptides showed alpha-helical conformation in all solvents except of pure buffer. The conformation of these peptides correlated well with the secondary structure obtained by homology modelling and even more striking with the X-ray structure of adenylate kinase, which was published recently. In contrast, three peptides, which were suggested to adopt no helical conformation did not show any content of alpha-helicity in any of the solvents that we investigated. One peptide, which contains a beta-sheet according to the X-ray analysis revealed a high content of beta-conformation by CD in buffer and in mixtures with trifluoroethanol. The two other peptides revealed mainly random coil in all solvents which we investigated. Therefore, we conclude that synthetic peptides are suitable tools to investigate the secondary structure of protein segments and that this conformation is frequently preserved in the intact protein.
报道了猪腺苷酸激酶（AK 1）的13个片段的合成，每个片段由15个残基组成，覆盖AK 1的整个序列。这些肽通过采用Fmoc/叔丁基策略的多步肽合成获得。为了通过圆二色光谱进行构象分析，使用了磷酸盐缓冲液（pH 7）、三氟乙醇和甲醇的不同混合物。除了纯缓冲液外，十种肽在所有溶剂中均呈现α-螺旋构象。这些肽的构象与通过同源建模获得的二级结构相关性良好，与最近发表的腺苷酸激酶的X射线结构相关性更强。相比之下，三种被认为不采用螺旋构象的肽在我们研究的任何溶剂中均未显示出任何α-螺旋含量。根据X射线分析含有β-折叠的一种肽在缓冲液以及与三氟乙醇的混合物中通过圆二色光谱显示出高含量的β-构象。另外两种肽在我们研究的所有溶剂中主要呈现无规卷曲。因此，我们得出结论，合成肽是研究蛋白质片段二级结构的合适工具，并且这种构象在完整蛋白质中经常得以保留。
