Navigating the structural landscape of de novo α–helical bundles
Navigating the structural landscape of de novo α–helical bundles
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DOI：
10.1101/503698
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发表时间：
2018-12
期刊：
影响因子：
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通讯作者：
G. G. Rhys-G.;Christopher W Wood;J. L. Beesley;N. Zaccai;A. Burton;R. L. Brady;Andrew R. Thomson;D. N. Woolfson
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文献类型：
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作者：
G. G. Rhys-G.;Christopher W Wood;J. L. Beesley;N. Zaccai;A. Burton;R. L. Brady;Andrew R. Thomson;D. N. Woolfson
两亲性α螺旋在水中的缔合导致α-螺旋束蛋白质结构。然而，这种驱动力-疏水效应-并不是特异性的，也没有定义相关状态下螺旋的数量或方向。相反，这是通过更深层次的序列与结构的关系来实现的，这种关系越来越被人们所认识。例如，对于一种结构极端但却普遍存在的螺旋-α-螺旋卷曲螺旋，已经建立了区分所有平行二聚体、三聚体和四聚体的关系。在此之上的缔合状态是已知的，螺旋的反平行和混合排列也是已知的。然而，这些替代状态不太好理解。在这里，我们描述了一个合成的肽系统，平行的六聚体和各种向上-向下-向上-向下四聚体之间的开关，以响应单个氨基酸的变化和解决方案的条件。每个肽变体的主要可接近状态在溶液中完全表征，并且在大多数情况下，以高分辨率X射线晶体结构表征。对这些结构的分析和检查有助于合理化所形成的不同状态。这种导航的结构景观的α-螺旋卷曲螺旋以上的二聚体和三聚体，在自然界中占主导地位，使我们能够合理地设计一个明确的和超稳定的反平行卷曲螺旋四聚体（apCC-Tet）。这种强大的从头蛋白质为蛋白质工程和合成生物学中的进一步结构和功能设计提供了另一种支架。
The association of amphipathic α helices in water leads to α-helical-bundle protein structures. However, the driving force for this—the hydrophobic effect—is not specific and does not define the number or the orientation of helices in the associated state. Rather, this is achieved through deeper sequence-to-structure relationships, which are increasingly being discerned. For example, for one structurally extreme but nevertheless ubiquitous class of bundle—the α-helical coiled coils—relationships have been established that discriminate between all-parallel dimers, trimers and tetramers. Association states above this are known, as are antiparallel and mixed arrangements of the helices. However, these alternative states are less-well understood. Here, we describe a synthetic-peptide system that switches between parallel hexamers and various up-down-up-down tetramers in response to single-amino-acid changes and solution conditions. The main accessible states of each peptide variant are characterized fully in solution and, in most cases, to high-resolution X-ray crystal structures. Analysis and inspection of these structures helps rationalize the different states formed. This navigation of the structural landscape of α-helical coiled coils above the dimers and trimers that dominate in nature has allowed us to design rationally a well-defined and hyperstable antiparallel coiled-coil tetramer (apCC-Tet). This robust de novo protein provides another scaffold for further structural and functional designs in protein engineering and synthetic biology.