Observation of α-Helical Hydrogen-Bond Cooperativity in an Intact Protein

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• 作者：Jingwen Li ; Yefei Wang ; Jingfei Chen ; Zhijun Liu ; Ad Bax ; Lishan Yao
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：February 17, 2016
• 年：2016
• 卷：138
• 期：6
• 页码：1824-1827
• 全文大小：328K
• ISSN：1520-5126

文摘

The presence and extent of hydrogen-bonding (H-bonding) cooperativity in proteins remains a fundamental question, which in the past has been studied extensively, mostly by infrared and fluorescence measurements on model peptides. We demonstrate that such cooperativity can be studied in an intact protein by hydrogen/deuterium exchange NMR spectroscopy. The method is based on the fact that substitution of NH by ND in a backbone amide group slightly weakens the N–H···O═C hydrogen bond. Our results show that such substitution at position i in an α-helix impacts the ¹H and ¹⁵N chemical shifts of the amide sites of residues i – 3 to i + 3. Quantum mechanical calculations indicate that the upfield shifts of ¹H and ¹⁵N resonances at site i, observed upon H/D exchanges at sites i – 3, i + 1, i + 2, and i + 3, correspond to a decrease of the ith backbone amide electric dipole moment, which weakens its H-bonding and long-range electrostatic interactions with other backbone amides in the α-helix. These results provide new quantitative insights into the cooperativity of H-bonding in protein α-helices.