Real-Time 1H NMR Reveals Position and Sequence Dependences of Amino Acid Isomerization in Amyloid Beta Fragments in Situ
Real-Time 1H NMR Reveals Position and Sequence Dependences of Amino Acid Isomerization in Amyloid Beta Fragments in Situ
复制标题
DOI：
10.1016/j.molliq.2022.120050
复制
发表时间：
2022-08
影响因子：
6
通讯作者：
Kenzo Aki;E. Okamura
中科院分区：
文献类型：
--
作者：
Kenzo Aki;E. Okamura
氨基酸异构体及其生物学相关功能已在生命系统中的多种肽和蛋白质中发现。然而，具体说明每个氨基酸的异构化如何在原位独立进行是具有挑战性的。在这项工作中，通过使用溶液态 1 H NMR 原位实时同时定量多个残基的氨基酸异构化。 NMR 区分异构化产物和反应物的能力在淀粉样β (Aβ) 1-40 片段中的天冬氨酰 (Asp) 残基以及谷氨酰 (Glu) 残基的不同位置得到了证明。这使我们能够根据异构化动力学实时系统地比较各种 Aβ 片段中 Asp1、Asp7、Asp23 和 Glu3 的异构化。研究发现，尽管 Asp23 和 Glu3 的反应活性有限，但 Asp1 和 Asp7 易于转化为异天冬氨酰 (isoAsp) 形式。分析证明了组氨酸 (His) 在调节 Asp 异构化中的作用； His6 和 His13/14 分别通过形成 Asp-His 复合物来减缓 Asp 向 isoAsp 的转化，从而分别对 Asp1 和 Asp7 的异构化进程显示出抑制作用。
Amino acid isomers and their biologically relevant functions have been found in a variety of peptides and proteins in a living system. It is challenging, however, to specify how such isomerization proceeds at each amino acid independently in situ. In this work, the amino acid isomerization was quantified simultaneously at multiple residues in real time, by using solution-state1H NMR in situ. The ability of NMR to distinguish isomerization product and reactant was demonstrated at different positions of aspartyl (Asp) residues in amyloid beta (Aβ) 1–40 fragments, as well as the glutamyl (Glu) residue. This enabled us to compare the isomerization of Asp1, Asp7, and Asp23, and Glu3 systematically in various Aβ fragments, in terms of the kinetics of isomerization in real time. It was found that Asp1 and Asp7 were prone to convert toiso-aspartyl (isoAsp) form, although Asp23 and Glu3 showed limited reactivity. The analysis demonstrated the role of histidine (His) in regulating Asp isomerization; His6 and His13/14 showed an inhibitory effect on the progress of isomerization at Asp1 and Asp7, respectively, by forming Asp-His complex that serves to slow down the conversion from Asp to isoAsp.