Mattos C, Petsko G A, Karplus M
Rosenstiel Basic Medical Sciences Research Center Brandeis University, Waltham, MA 02254-9110.
J Mol Biol. 1994 May 20;238(5):733-47. doi: 10.1006/jmbi.1994.1332.
The conformational properties of tight two-residue beta-turns in proteins are examined by empirical energy function calculations. Twenty-five tight turns are studied in isolation, in the presence of the protein, and in the presence of the protein and crystal water molecules. The conformational properties are subdivided into those that are intrinsic to the turn and those that depend on the protein and water environment. Two factors are shown to determine the conformation of a tight beta-turn. One is the twist of the beta-sheet (responsible for selecting either a type I' or II' conformation as opposed to the more common types I or II) and the other is a local electrostatic effect (responsible for distinguishing between the type I' and II' conformations). In the rare cases where a two-residue turn is found in a type I conformation, there exists a stabilizing feature (turn-protein interaction, a side-chain in a conformation that stabilizes type I, etc.) which compensates for the unfavorable twist of the turn relative to the beta-sheet.
通过经验能量函数计算研究了蛋白质中紧密双残基β-转角的构象性质。分别对25个紧密转角进行了研究，包括孤立状态下、存在蛋白质时以及存在蛋白质和晶体水分子时的情况。构象性质被细分为转角固有的性质以及依赖于蛋白质和水环境的性质。结果表明有两个因素决定紧密β-转角的构象。一个是β-折叠的扭曲（决定选择I'型或II'型构象，而非更常见的I型或II型），另一个是局部静电效应（用于区分I'型和II'型构象）。在罕见的情况下，若双残基转角呈I型构象，则存在一种稳定特征（转角-蛋白质相互作用、稳定I型构象的侧链构象等），可弥补该转角相对于β-折叠不利的扭曲。
