Deprotonation of a Single Amino Acid Residue Induces Significant Stability in an α-Helical Heteropeptide
Deprotonation of a Single Amino Acid Residue Induces Significant Stability in an α-Helical Heteropeptide
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DOI：
10.1021/acs.jpcb.8b07418
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发表时间：
2018-12-13
影响因子：
3.3
通讯作者：
Kuczera, Krzysztof
中科院分区：
文献类型：
--
作者：
Jas, Gouri S.;Kuczera, Krzysztof
二级结构元件的稳定性是结构稳定蛋白质的重要组成部分。残基序列中质子的存在及其直接环境在构象稳定性中起着重要作用。在这项研究中，我们表明，与未质子化的形式相比，从单个氨基酸残基中去除质子显着提高了螺旋杂肽的稳定性。远紫外圆二色光谱、荧光光谱、荧光能量转移测量和超过 10 μs 的全原子分子动力学模拟用于提供该事件的原子级详细 0 表征。在所研究的 α 螺旋肽序列中，N 端有一个组氨酸残基，它与位于四个残基之外的色氨酸相互作用，并在质子化时猝灭荧光。从该组氨酸残基中去除质子可以消除色氨酸荧光，并有助于显着增加螺旋稳定性。对各个残基构象的原子详细分析表明，质子化的组氨酸往往更接近色氨酸，这与肽 N 和 C 末端较高的螺旋含量以及肽中心区域较低的螺旋含量相关。在中性组氨酸存在的情况下，当色氨酸荧光不再被猝灭并且组氨酸进一步远离色氨酸时，N-和-C末端的螺旋含量基本保持不变，并且在中心区域显着增加。我们的结果强烈表明，与中性组氨酸残基相比，色氨酸与质子化组氨酸的相互作用下调了螺旋结构中心段的螺旋群。在中性组氨酸残基存在的情况下，上调该 α 螺旋杂肽中心片段的螺旋群显着增加了肽结构稳定性。
Stability of secondary structural elements is an integral component of a structurally stable protein. Presence of protons in the residue sequence and their immediate environment play a significant role in conformational stability. In this study, we show that removing a proton from a single amino acid residue significantly increases the stability of an a helical heteropeptide in comparison with the unprotonated form. Far-UV circular dichroism spectroscopy, fluorescence spectroscopy, fluorescence energy transfer measurements, and over 10 mu s of all-atom molecular dynamics simulations are used to provide an atomically detailed 0 characterization of this event. There is a single histidine residue in the studied alpha-helical peptide sequence toward the N-terminal that interacts with a tryptophan located four residues away and quenches the fluorescence when protonated. Removing a proton from this histidine residue dequenches the tryptophan fluorescence and contributes to a significant increase in the helix stability. Atomically detailed analysis of individual residue conformations shows that the protonated histidine tends to be in closer proximity to the tryptophan, which correlates with higher helix content in the N and C termini and lower helix content in the central region of the peptide. In the presence of a neutral histidine, when tryptophan fluorescence is no longer quenched and histidine moves further away from tryptophan, the helix content remains mostly unchanged in the N-and-C termini and significantly increases in the central region. Our results strongly suggest that interactions of the tryptophan with a protonated histidine downregulate the helix population in the central segment of the helical structure compared to a neutral histidine residue. Upregulation of helix population of the central segment of this alpha-helical heteropeptide in the presence of a neutral histidine residue significantly increases the peptide structural stability.