Mechanisms of hydrogen exchange in proteins from nuclear magnetic resonance studies of individual tryptophan indole NH hydrogens in lysozyme.
Mechanisms of hydrogen exchange in proteins from nuclear magnetic resonance studies of individual tryptophan indole NH hydrogens in lysozyme.
复制标题
溶菌酶中单个色氨酸吲哚 NH 氢的核磁共振研究蛋白质中氢交换的机制。
DOI：
10.1021/bi00534a042
复制
发表时间：
1982
期刊：
影响因子：
2.9
通讯作者：
Poulsen,FM
中科院分区：
文献类型：
--
作者：
Wedin,RE;Delepierre,M;Dobson,CM;Poulsen,FM
Randall E. Wedin、Muriel Delepierre、1 Christopher M. Dobson,*-1* 和 Flemming M. Poulsen8 摘要：已使用 NMR 在很宽的温度范围内测量了 2H20 中溶菌酶的六个色氨酸吲哚 NH 氢的单独溶剂交换速率。已经确定了两种不同的交换机制，一种以高活化能为特征，另一种以低得多的活化能为特征。高能过程已被证明与蛋白质的协同热解折叠直接相关，并且是即使在比变性温度低 15°C 的情况下交换最慢的氢的主要机制。正如各种实验和理论技术所揭示的那样，溶液中的折叠和Koteins的速率常数和活化能经历广泛的分子运动（Karplus和McCammon，1981）。蛋白质运动的一些最初证据来自于对球状蛋白质中氢交换的观察（Hvidt & Linderstrom-Lang，1954）。在氢交换中，不稳定的氢（例如，来自蛋白质主链的酰胺氢或来自色氨酸侧链的吲哚NH氢）被来自溶剂的氢取代。如果使用氘或氚标记的溶剂，则可以直接测量交换速率。交换所需的时间可以从几秒到几年不等，具体取决于 pH 值和温度等条件 (Hvidt & Nielsen, 1966)。在过去的 20 年中，人们进行了大量有关氢交换率与蛋白质运动的研究（Hvidt & Nielsen，1966；Englander 等，1972；Woodward & Hilton，1979）。两步反应方案通常用于解释天然蛋白质中的氢交换现象。该方案的第一步代表使可交换基团和溶剂接触的反应，第二步是化学交换步骤。已经提出了几种模型来解释该反应方案第一步的物理性质。各种模型中的哪一个最能描述给定条件下的氢交换机制是当前存在争议的问题。在一种模型中，溶剂分子通过小分子波动打开的空腔渗透到蛋白质基质的内部，并在蛋白质内部发生交换。该模型最近被用于
Randall E. Wedin, Muriel Delepierre, 1 Christopher M. Dobson,*-1* and Flemming M. Poulsen8 abstract: The individual rates of solvent exchange of the six tryptophan indole NH hydrogens of lysozyme in 2H20 have been measured over a wide range of temperatures by using NMR. Two distinct mechanisms for exchange have been identified, one characterized by a high activation energy and the other by a much lower activation energy. The high-energy process has been shown to be associated directly with the cooperative thermal unfolding of the protein and is the dom-inant mechanism for exchange of the most slowly exchanging hydrogen even 15 C below the denaturation temperature. Rate constants and activation energies for the folding and^ Koteins in solution undergo a wide range of molecular motions as revealed by a variety of experimental and theo-retical techniques (Karplus & McCammon, 1981). Some of the first evidence for proteinmotions came from the obser-vation of hydrogen exchange in globular proteins (Hvidt & Linderstrom-Lang, 1954). In hydrogen exchange, labile hydrogens (eg, amide hydrogens from the protein backbone or indole NH hydrogens from tryptophan side chains) are re-placed by hydrogens from the solvent. If deuterium-or tri-tium-labeled solvent is used, the rates of exchange can be measured directly. The time required for exchange can range from seconds to yearsdepending upon conditions such as pH and temperature (Hvidt & Nielsen, 1966). Over the last 2 decades, much research has been done relating hydrogenexchange rates with protein motions (Hvidt & Nielsen, 1966; Englander et al., 1972; Woodward & Hilton, 1979). A two-step reaction scheme has generally been used to explain the phenomenon of hydrogen exchange in native proteins. The first step in this scheme represents the reactions bringing the exchangeable groups and solvent into contact, the second step being thechemical exchange step. Several models have been proposed to explain the physical nature of the first step in this reaction scheme. The question of which of the various models best describes the mechanism of hydrogen exchange under given conditions is a matter of current con-troversy. In one model, the solvent molecules penetrate into the interior of the protein matrix throughcavities opened by small molecular fluctuations, and exchange takes place in the interior of the protein. This model has recently been used to