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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Helix-Coil Transition at a Glycine Following a Nascent alpha-Helix: A Synergetic Guidance Mechanism for Helix Growth
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Helix-Coil Transition at a Glycine Following a Nascent alpha-Helix: A Synergetic Guidance Mechanism for Helix Growth

机译：螺旋线圈在新生alpha-helix后的甘氨酸转变：螺旋增长的协同指导机制

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摘要

A detailed understanding of forces guiding the rapid folding of a polypeptide from an apparently random coil state to an ordered alpha-helical structure following the rate-limiting preorganization of the initial three residue backbones into helical conformation is imperative to comprehending and regulating protein folding and for the rational design of biological mimetics. However, several details of this process are still unknown. First, although the helix-coil transition was proposed to originate at the residue level (J. Chem. Phys. 1959, 31, 526-535; J. Chem. Phys. 1961, 34, 1963-1974), all helix-folding studies have only established it between time-averaged bulk states of a long-lived helix and several transiently populated random coils, along the whole helix model sequence. Second, the predominant thermodynamic forces driving either this two-state transition or the faster helix growth following helix nucleation are still unclear. Third, the conformational space of the random coil state is not well-defined unlike its corresponding alpha-helix. Here we investigate the restrictions placed on the conformational space of a Gly residue backbone, as a result of it immediately succeeding a nascent ahelical turn. Analyses of the temperature-dependent ID-, 2D-NMR, FT-IR, and CD spectra and GROMACS MD simulation trajectory of a Gly residue backbone following a model alpha-helical turn, which is artificially rigidified by a covalent hydrogen bond surrogate, reveal that: (i) the alpha-helical turn guides the phi torsion of the Gly exclusively into either a predominantly populated entropically favored alpha-helical (alpha-phi) state or a scarcely populated random coil (RC-phi) state; (ii) the alpha-phi state of Gly in turn favors the stability of the preceding alpha-helical turn, while the RC-phi state disrupts it, revealing an entropy-driven synergetic guidance for helix growth in the residue following helix nucleation. The applicability of a current synergetic guidance mechanism to explain rapid helix growth in folded and unfolded states of proteins and helical peptides is discussed.
机译：对引导多肽的快速折叠从明显随机卷状态到有序α-螺旋结构的力的详细了解，在初始三个残留骨架的速率限制到螺旋构象之后是理解和调节蛋白质折叠和蛋白质折叠的必要条件生物学模拟物的合理设计。但是，这个过程的几个细节仍然是未知的。首先，虽然提出了螺旋线圈转变来源于残留水平（J.Chem. phystem.759,31,526-535; J.Chem。物理。761,34,1963-1974），所有螺旋折叠研究沿着整个螺旋模型序列，仅在长期螺旋和几个瞬时填充的随机线圈之间建立了它的时间平均散装状态。其次，驱动这种双态转变或螺旋成核后的螺旋生长的主要热力学力仍然不明朗。第三，与其相应的alpha-helix不同，无随机线圈状态的构象空间并不定制。在这里，我们调查放置在Gly残留骨架的构象空间的限制，因为它立即成功地成功地达到了肛门转弯。在模型α-螺旋转弯后，通过共价氢键替代，揭示α-螺旋转弯后的温度依赖性ID-，2D-NMR，FT-IR和CD谱和Gromacs MD模拟轨迹的Gly残留骨架模拟轨迹。那是：（i）α-螺旋转向将甘氏肌肉的PHI扭转专门引导到主要植物熵最有利的α-螺旋（α-PHI）状态或几乎填充的无规卷（RC-PHI）状态; （ii）（ii）α-Phi状态反过来依赖于前面的α-螺旋转弯的稳定性，而RC-PHI态会破坏它，揭示螺旋成核后残留物中螺旋生长的熵驱动的协同指导。讨论了当前协同指导机制的适用性来解释折叠和呈螺旋肽型蛋白质和螺旋肽的快速螺旋生长。

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