Evaluating β-turn mimics as β-sheet folding nucleators
Evaluating β-turn mimics as β-sheet folding nucleators
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DOI：
10.1073/pnas.0813012106
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发表时间：
2009-07-07
影响因子：
11.1
通讯作者：
Kelly, Jeffery W.
中科院分区：
文献类型：
--
作者：
Fuller, Amelia A.;Du, Deguo;Kelly, Jeffery W.
-转是一种常见的构象，使蛋白质能够采用球形结构，它们的形成通常限制了折叠的速率。β -turn模拟物，取代β -turn的i + 1和i + 2氨基酸残基的分子，被设想通过预先组织垂坠多肽链作为折叠成核剂，从而降低β -片形成的激活屏障。然而，证明β -转模拟物在协同折叠蛋白质中可以作为强成核体的关键动力学实验尚未报道。我们结合了6个β -turn模拟物，模拟了不同的β -turn类型，以代替Pin - 1 WW结构域（一种三链β -sheet蛋白）的工程β -turn 1或β -bulge turn 1中的2个残基。我们提出了2条动力学证据，表明β -turn模拟物的包含改变了β -sheet折叠速率，使我们能够将β -turn模拟物分为3类：弱成核但允许Pin - WW折叠的成核物、原生成核物和强成核物。相对于包含所有α -氨基酸序列的WW结构域，强核子加速折叠。溶液核磁共振结构表明，在加入强e -烯烃成核剂后，保留了天然Pin WW β -片结构。这些β -转模拟物现在可用于询问蛋白质折叠过渡态结构，并且提出的2个动力学分析可用于评估其他β -转模拟物的成核能力。
beta-Turns are common conformations that enable proteins to adopt globular structures, and their formation is often rate limiting for folding. beta-Turn mimics, molecules that replace the i + 1 and i + 2 amino acid residues of a beta-turn, are envisioned to act as folding nucleators by preorganizing the pendant polypeptide chains, thereby lowering the activation barrier for beta-sheet formation. However, the crucial kinetic experiments to demonstrate that beta-turn mimics can act as strong nucleators in the context of a cooperatively folding protein have not been reported. We have incorporated 6 beta-turn mimics simulating varied beta-turn types in place of 2 residues in an engineered beta-turn 1 or beta-bulge turn 1 of the Pin 1 WW domain, a three-stranded beta-sheet protein. We present 2 lines of kinetic evidence that the inclusion of beta-turn mimics alters beta-sheet folding rates, enabling us to classify beta-turn mimics into 3 categories: those that are weak nucleators but permit Pin WW folding, native-like nucleators, and strong nucleators. Strong nucleators accelerate folding relative to WW domains incorporating all alpha-amino acid sequences. A solution NMR structure reveals that the native Pin WW beta-sheet structure is retained upon incorporating a strong E-olefin nucleator. These beta-turn mimics can now be used to interrogate protein folding transition state structures and the 2 kinetic analyses presented can be used to assess the nucleation capacity of other beta-turn mimics.