Kim C A, Berg J M
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218.
Nature. 1993 Mar 18;362(6417):267-70. doi: 10.1038/362267a0.
The three-dimensional structures of proteins reveal that the distribution of amino acids within the major classes of secondary structure is not random but that each amino acid has its own preferred secondary structural arrangements. Propensity scales for residues in alpha-helices have been generated through the use of various host-guest systems. Here we measure the thermodynamic beta-sheet propensities of each of the twenty commonly occurring amino acids. A previously studied zinc-finger peptide was used as the host system in which amino acids were substituted into a guest site, a solvent-exposed position in an antiparallel beta-sheet. As these peptides are unfolded in the absence of bound metal but are folded in their presence, it is assumed that the thermodynamics of metal binding fully reflect peptide-folding energy. A competitive cobalt(II)-binding assay was used to determine these energies with high precision. The relative free energies correlate well with previously derived potential values based on statistical analysis of protein structures. We are therefore able to present a thermodynamic beta-sheet propensity scale for all the commonly occurring amino acids in aqueous solution.
蛋白质的三维结构表明，在主要二级结构类型中氨基酸的分布并非随机，而是每种氨基酸都有其偏好的二级结构排列。通过使用各种主客体系统，已生成了α-螺旋中残基的倾向量表。在此，我们测量了二十种常见氨基酸各自的热力学β-折叠倾向。一种先前研究过的锌指肽被用作主体系统，其中氨基酸被替换到客体位点，即反平行β-折叠中一个暴露于溶剂的位置。由于这些肽在没有结合金属时是展开的，但在有金属时会折叠，所以假定金属结合的热力学完全反映了肽折叠的能量。采用竞争性钴（II）结合测定法高精度地确定这些能量。相对自由能与基于蛋白质结构统计分析先前得出的势能值密切相关。因此，我们能够给出水溶液中所有常见氨基酸的热力学β-折叠倾向量表。
