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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >End-to-end distance distributions and intrachain diffusion constants in unfolded polypeptide chains indicate intramolecular hydrogen bond formation
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End-to-end distance distributions and intrachain diffusion constants in unfolded polypeptide chains indicate intramolecular hydrogen bond formation

机译：未折叠多肽链中的端到端距离分布和链内扩散常数表明分子内氢键形成

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摘要

Characterization of the unfolded state is essential for the understanding of the protein folding reaction. We performed timeresolved FRET measurements to gain information on the dimensions and the internal dynamics of unfolded polypepticle chains. Using an approach based on global analysis of data obtained from two different donor-acceptor pairs allowed for the determination of distance distribution functions and diffusion constants between the chromophores. Results on a polypepticle chain consisting of 16 Gly-Ser repeats between the FRET chromophores reveal an increase in the average end-to-end distance from 18.9 to 39.2 angstrom between 0 and 8 M GdmCl. The increase in chain dimensions is accompanied by an increase in the end-to-end diffusion constant from (3.6 +/- 1.0) X 10(-7) cm(2) S-1 in water to (14.8 +/- 2.5) x 10(-7) cm(2) s(-1) in 8 M Gc1mCl. This finding suggests that intrachain interactions in water exist even in very flexible chains lacking hydrophobic groups, which indicates intramolecular hydrogen bond formation. The interactions are broken upon denaturant binding, which leads to increased chain flexibility and longer average end-to-end distances. This finding implies that rapid collapse of polypepticle chains during refolding of denaturant-unfolded proteins is an intrinsic property of polypepticle chains and can, at least in part, be ascribed to nonspecific intramolecular hydrogen bonding. Despite decreased intrachain diffusion constants, the conformational search is accelerated in the collapsed state because of shorter diffusion distances. The measured distance distribution functions and diffusion constants in combination with Szabo-SchultenSchulten theory were able to reproduce experimentally determined rate constants for end-to-end loop formation.
机译：展开状态的表征对于理解蛋白质折叠反应至关重要。我们进行了时间分辨的FRET测量，以获取有关未折叠的多菌链的尺寸和内部动力学的信息。使用基于对从两个不同的供体-受体对获得的数据进行全局分析的方法，可以确定生色团之间的距离分布函数和扩散常数。由FRET生色团之间的16个Gly-Ser重复序列组成的多消化链的结果表明，0至8 M GdmCl之间的平均端对端距离从18.9埃增加到39.2埃。链尺寸的增加伴随着端到端扩散常数的增加，从（3.6 +/- 1.0）X 10（-7）cm（2）S-1在水中增加到（14.8 +/- 2.5）在8 M Gc1mCl中x 10（-7）cm（2）s（-1）该发现表明即使在缺乏疏水基团的非常柔性的链中也存在水中的链内相互作用，这表明分子内氢键形成。变性剂结合会破坏相互作用，从而增加链的柔韧性和更长的平均端到端距离。该发现暗示在变性剂未折叠的蛋白质的重折叠过程中，多消化链的快速塌陷是多消化链的固有特性，并且可以至少部分地归因于非特异性分子内氢键。尽管链内扩散常数降低，但由于较短的扩散距离，构象搜索在折叠状态下得以加速。结合Szabo-SchultenSchulten理论，测得的距离分布函数和扩散常数能够重现实验确定的速率常数，以形成端到端的回路。

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