Department of Chemistry, University of Cambridge, MRC Centre for Protein Engineering, Lensfield Rd, Cambridge CB2 1EW UK.
Nature. 2010 Feb 4;463(7281):685-8. doi: 10.1038/nature08743.
Energy landscape theory is a powerful tool for understanding the structure and dynamics of complex molecular systems, in particular biological macromolecules. The primary sequence of a protein defines its free-energy landscape and thus determines the folding pathway and the rate constants of folding and unfolding, as well as the protein's native structure. Theory has shown that roughness in the energy landscape will lead to slower folding, but derivation of detailed experimental descriptions of this landscape is challenging. Simple folding models show that folding is significantly influenced by chain entropy; proteins in which the contacts are local fold quickly, owing to the low entropy cost of forming stabilizing, native contacts during folding. For some protein families, stability is also a determinant of folding rate constants. Where these simple metrics fail to predict folding behaviour, it is probable that there are features in the energy landscape that are unusual. Such general observations cannot explain the folding behaviour of the R15, R16 and R17 domains of alpha-spectrin. R15 folds approximately 3,000 times faster than its homologues, although they have similar structures, stabilities and, as far as can be determined, transition-state stabilities. Here we show that landscape roughness (internal friction) is responsible for the slower folding and unfolding of R16 and R17. We use chimaeric domains to demonstrate that this internal friction is a property of the core, and suggest that frustration in the landscape of the slow-folding spectrin domains may be due to misdocking of the long helices during folding. Theoretical studies have suggested that rugged landscapes will result in slower folding; here we show experimentally that such a phenomenon directly influences the folding kinetics of a 'normal' protein, that is, one with a significant energy barrier that folds on a relatively slow, millisecond-second, timescale.
能量景观理论是理解复杂分子系统（尤其是生物大分子）结构和动力学的有力工具。蛋白质的一级序列决定了其自由能景观，从而决定了折叠途径和折叠、展开的速率常数，以及蛋白质的天然结构。理论表明，能量景观的粗糙度会导致折叠速度变慢，但对这种景观进行详细的实验描述具有挑战性。简单的折叠模型表明，折叠受到链熵的显著影响；在折叠过程中，由于形成稳定的天然接触所需的熵成本较低，局部接触的蛋白质会快速折叠。对于某些蛋白质家族，稳定性也是折叠速率常数的决定因素。在这些简单的指标无法预测折叠行为的情况下，很可能存在能量景观中的不寻常特征。这些一般性观察结果无法解释 α- spectrin 的 R15、R16 和 R17 结构域的折叠行为。尽管 R15 的结构、稳定性与其同源物相似，而且在可以确定的情况下，其过渡态稳定性也相似，但它的折叠速度却比其同源物快约 3000 倍。在这里，我们表明景观粗糙度（内部摩擦）是导致 R16 和 R17 折叠和展开速度较慢的原因。我们使用嵌合体结构域证明，这种内部摩擦是核心的一个特性，并提出在折叠过程中长螺旋的错误对接可能导致慢折叠 spectrin 结构域的景观受挫。理论研究表明，崎岖的景观会导致折叠速度变慢；在这里，我们通过实验表明，这种现象直接影响了一种“正常”蛋白质的折叠动力学，即具有显著能量障碍的蛋白质，其折叠速度较慢，在毫秒到秒的时间尺度上。
Zotero 插件
