Side-chain effects on peptidyl-prolyl cis/trans isomerisation
Side-chain effects on peptidyl-prolyl cis/trans isomerisation
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DOI：
10.1006/jmbi.1998.1770
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发表时间：
1998-06-05
影响因子：
5.6
通讯作者：
Fischer, G
中科院分区：
文献类型：
--
作者：
Reimer, U;Scherer, G;Fischer, G
肽基脯氨酰顺/反异构化经常被发现是蛋白质折叠的限速步骤。为了确定脯氨酸前面的氨基酸的性质是否控制天然蛋白质中顺式脯氨酰键的可能性，对五肽系列Ac-Ala-Xaa-Pro-Ala-Lys-NH 2中脯氨酰异构化的热力学和动力学进行了系统的研究。所有蛋白质氨基酸在脯氨酸之前的位置被取代。当通过H-1-NMR和CD光谱测量时，这两种异构体被证明在水溶液中的寡肽的整个系列中没有有序结构。因此，异构化率和顺/反比计算溶剂跳跃和H-1-NMR磁化转移实验排他地反映了侧链效应的Xaa位置的肽系列。寡肽中的顺式含量与蛋白质中Xaa-Pro顺式脯氨酰键的倾向之间存在粗略的相关性。这种相关性表明脯氨酰键的构象主要是由蛋白质中的局部效应决定的。在4 ℃时，脯氨酸之前含有未电离氨基酸的五肽的速率常数k（c-->t）范围为3.2 x 10（-3）s（-1）（Xaa=Ala）至0.5 x 10（-3）s（-1）（Xaa = Trp）。脯氨酸聚类导致的异构化循环表明旋转键侧翼的肽键构象的异构化率有相当大的影响。酪氨酸和组氨酸都通过其各自侧链的去质子化特异性地降低异构化速率几倍。(C)出版社：Academic Press Limited。
Peptidyl-prolyl cis/trans isomerisation has been frequently found as a rate Limiting step in the folding of proteins. In order to determine whether the nature of the amino acid preceding proline controls the probability of cis prolyl bonds in native proteins, systematic studies on the thermodynamics and kinetics of the prolyl isomerisation in the pentapeptide series Ac-Ala-Xaa-Pro-Ala-Lys-NH2 were performed. All proteinogenic amino acids were substituted in the position preceding proline. When measured by H-1-NMR and CD spectroscopy both isomers proved to be devoid of ordered structure in the whole series of the oligopeptides in aqueous solution. Thus, isomerization rates and cis/trans ratios calculated from solvent jump and H-1-NMR magnetisation transfer experiments exclusively reflect the side-chain effects of the Xaa position in the peptide series. There is a rough correlation between the cis content in the oligopeptides and the propensity of Xaa-Pro cis prolyl bonds in proteins. This correlation suggests that the prolyl bond conformation is mainly determined by local effects in proteins. The rate constants k(c-->t) of pentapeptides containing unionised amino acids preceding proline range from 3.2 x 10(-3) s(-1) (Xaa=Ala) to 0.5 x 10(-3) s(-1) (Xaa = Trp) at 4 degrees C. Proline clustering led to an isomerisation cycle indicating considerable influence on the isomerisation rates of the peptide bond conformations flanking the rotating bond. Both tyrosine and histidine specifically reduce isomerisation rates severalfold by deprotonation of their respective side-chains. (C) 1998 Academic Press Limited.