HYDROXYL HYDROGEN CONFORMATIONS IN TRYPSIN DETERMINED BY THE NEUTRON-DIFFRACTION SOLVENT DIFFERENCE MAP METHOD - RELATIVE IMPORTANCE OF STERIC AND ELECTROSTATIC FACTORS IN DEFINING HYDROGEN-BONDING GEOMETRIES
HYDROXYL HYDROGEN CONFORMATIONS IN TRYPSIN DETERMINED BY THE NEUTRON-DIFFRACTION SOLVENT DIFFERENCE MAP METHOD - RELATIVE IMPORTANCE OF STERIC AND ELECTROSTATIC FACTORS IN DEFINING HYDROGEN-BONDING GEOMETRIES
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DOI：
10.1073/pnas.87.12.4468
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发表时间：
1990-06-01
影响因子：
11.1
通讯作者：
SINTCHAK, MD
中科院分区：
文献类型：
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作者：
KOSSIAKOFF, AA;SHPUNGIN, J;SINTCHAK, MD
中子衍射图已用于指定胰蛋白酶中羟基氢的转子构象。这些构象的知识用于评估空间效应和静电效应在赋予这些基团的氢结合几何形状方面的相对重要性。一个普遍的发现是，大多数羟基是旋转排序的，其最高填充构象接近低能交错取向。对于丝氨酸和苏氨酸的低能构象异构体（-60°、60°、180°），反式（-180°）位置最多，其次是+60°。在胰蛋白酶中，24 个丝氨酸中只有 1 个位于 -60°。构象者。丝氨酸羟基优先充当氢键受体，很少观察到单独作为氢键供体。发现苏氨酸比丝氨酸更有可能参与两个 H 键；发现酪氨酸更喜欢充当供体。在氢结合情况下，定义旋转势垒的能量与局部静电之间不相容，静电标准占主导地位。总的来说，这些发现支持氢键模型，其中低能羟基取向和局部静电环境之间存在很强的内在互补性。
Neutron diffraction maps have been used to assign the rotor conformations of the hydroxyl hydrogens in trypsin. Knowledge of these conformations is used to assess the relative importance of steric and electrostatic effects in conferring the H-binding geometries of these groups. A general finding was the most hydroxyl groups are rotationally ordered with their highest populated conformation near the low-energy staggered orientation. For the low-energy conformers (-60.degree., 60.degree., 180.degree.) of serine and threonine, the trans (-180.degree.) position is most highly populated followed by +60.degree.. In trypsin, only 1 of 24 serines was found in the -60.degree. conformer. Serine hydroxyls preferentially act as H-bond acceptors and rarely are observed as H-bond donors alone. Threonines were found to be more likely than serines to participate in two H bonds; tryosines were found to prefer to act as donors. In H-binding situations in which there was incompatibility between the energies defining the barrier to rotation and the local electrostatics, the electrostatic criteria dominated. Overall, the findings support a model of H bonding where there exists strong inherent complementarity between the low-energy hydroxyl orientations and the local electrostatic environment.