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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Stepwise helix formation and chain compaction during protein folding
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Stepwise helix formation and chain compaction during protein folding

机译：蛋白质折叠过程中逐步螺旋形成和链压紧

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One of the persistent problems in protein folding is understanding the relative importance of secondary and tertiary structure formation. Elements of secondary structure are stabilized primarily by interactions among amino acids that are close in sequence, whereas tertiary structure is supported by interactions among more distant segments of the chain. Therefore, it is reasonable to assume that folding is a hierarchical process with secondary structure preceding tertiary structure formation (1). In fact, fluctuating elements of secondary structure often persist under denaturing conditions where the chain is otherwise disordered and devoid of specific tertiary interactions. Numerous observations of helical structure in protein fragments and synthetic peptides further support the conclusion that secondary structure formation is governed by the local amino acid sequence context. Conversely, secondary structure elements are marginally stable in isolation and require stabilizing tertiary interactions to become persistent. Under physiological conditions, hydrophobic interactions among apolar side chains favor collapse of the polypeptide chain into a compact conformation, suggesting that solvent-induced chain collapse is a critical early step in folding. Such a hydrophobic collapse is likely to be accompanied by formation of hydrogen-bonded secondary structure to avoid the energetically unfavorable burial of polar backbone atoms (2). In a recent issue of PNAS, Uzawa et al. (3) presented evidence that compact structural ensembles rich in secondary structure can appear early in folding. They followed the formation of helical secondary structure and the decrease in chain dimensions throughout the folding reaction of apomyoglobin, covering the time range from ≈ 300 μs to 1 s.
机译：蛋白质折叠中的持续问题之一是理解二级和三级结构形成的相对重要性。二级结构的元素主要是通过序列紧密的氨基酸之间的相互作用来稳定的，而三级结构则是通过链的更远链段之间的相互作用来支持的。因此，可以合理地认为折叠是在三级结构形成之前具有二级结构的分层过程。实际上，二级结构的波动元素通常在变性条件下持续存在，在变性条件下，该链否则会无序且没有特定的三次相互作用。蛋白质片段和合成肽中螺旋结构的大量观察结果进一步支持了二级结构形成受局部氨基酸序列环境支配的结论。相反，二级结构元素在隔离方面略微稳定，需要稳定的第三级相互作用才能持久。在生理条件下，非极性侧链之间的疏水相互作用有利于多肽链塌陷成紧密构象，这表明溶剂诱导的链塌陷是折叠的关键早期步骤。这种疏水性塌陷很可能伴随着氢键键合的二级结构的形成，从而避免了极性主链原子在能量上的不利埋葬（2）。在最近一期的PNAS中，Uzawa等人。 （3）提出的证据表明，富含二级结构的紧凑结构体可以在折叠早期出现。他们遵循了螺旋二级结构的形成，并在整个apomyoglobin的折叠反应中链尺寸的减小，涵盖了从≈300μs到1 s的时间范围。

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