Intramolecular assistance of cis/trans isomerization of the histidine-proline moiety
Intramolecular assistance of cis/trans isomerization of the histidine-proline moiety
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DOI：
10.1021/bi9713916
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发表时间：
1997-11-11
期刊：
影响因子：
2.9
通讯作者：
Fischer, G
中科院分区：
文献类型：
--
作者：
Reimer, U;ElMokdad, N;Fischer, G
肽基-脯氨酰顺式/反式异构化是多肽骨架中缓慢的构象互变，通常限制蛋白质的重折叠速率，并被认为在蛋白质的细胞重组中发挥作用，为了探测位于脯氨酸附近的序列片段中的带正电的氨基酸的影响，含Arg-Pro和His-Pro的肽的旋转势垒通过异构体特异性蛋白水解和Suc-Ala-His-Pro-Phe-NH-Np，Ac-Ala-Arg-Pro-Ala-Lys-NH 2，Ac-Ala-His-Tro-Ala-Lys-NH 2、血管紧张素III、促甲状腺素释放激素（TRH）和[His（3-Me）（2）]TRH水溶液。与精氨酸的胍基相反，脯氨酸之前的组氨酸质子化侧链导致脯氨酰异构化相对于未质子化状态加速高达10倍。氨基酸序列中脯氨酸之后的精氨酸和组氨酸残基被证明是无效的。在碱性和酸性条件下，血管紧张素III的动力学溶剂氘同位素效应k（c-->t）（H2O）/k（c-->t）（D2 O）分别为1.0 +/- 0.1和2.0 +/- 0.1。结果解释在分子内一般酸催化脯氨酰键旋转的咪唑基团，这是没有先例的分子间催化。
Peptidyl-prolyl cis/trans isomerization is a slow conformational interconversion in the polypeptide backbone that is frequently rate-limiting in refolding of proteins and is thought to play a role in cellular restructuring of proteins, In order to probe the influence of positively charged amino acids located in sequence segments adjacent to proline, the rotational barriers of Arg-Pro-and His-Pro-containing peptides were determined by isomer-specific proteolysis and dynamic NMR spectroscopy for Suc-Ala-His-Pro-Phe-NH-Np, Ac-Ala-Arg-Pro-Ala-Lys-NH2, Ac-Ala-His-Tro-Ala-Lys-NH2, angiotensin III, thyrotropin-releasing hormone (TRH), and [His(3-Me)(2)]TRH in aqueous solution. Ln contrast to the guanidinium group of arginine, the protonated side chain of histidine preceding proline led to an acceleration of the prolyl isomerization up to 10-fold relative to the unprotonated state, Both arginine and histidine residues succeeding proline in an amino acid sequence proved to be ineffective. Under basic and acidic conditions the kinetic solvent deuterium isotope effects k(c-->t)(H2O)/k(c-->t)(D2O) for angiotensin III were 1.0 +/- 0.1 and 2.0 +/- 0.1, respectively. The results are interpreted In terms of intramolecular general acid catalysis of prolyl bond rotation by the imidazolium group that is without precedent in intermolecular catalysis.