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首页> 外文期刊>Journal of Molecular Biology >Observation of Continuous Contraction and a Metastable Misfolded State during the Collapse and Folding of a Small Protein
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Observation of Continuous Contraction and a Metastable Misfolded State during the Collapse and Folding of a Small Protein

机译：在坍塌和折叠折叠和折叠的小蛋白质期间观察连续收缩和亚稳定的状态

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To obtain proper insight into how structure develops during a protein folding reaction, it is necessary to understand the nature and mechanism of the polypeptide chain collapse reaction, which marks the initiation of folding. Here, the time-resolved fluorescence resonance energy transfer technique, in which the decay of the fluorescence light intensity with time is used to determine the time evolution of the distribution of intramolecular distances, has been utilized to study the folding of the small protein, monellin. It is seen that when folding begins, about one-third of the protein molecules collapse into a molten globule state (I-MG), from which they relax by continuous further contraction to transit to the native state. The larger fraction gets trapped into a metastable misfolded state. Exit from this metastable state occurs via collapse to the lower free energy I-MG state. This exit is slow, on a time scale of seconds, because of activation energy barriers. The trapped misfolded molecules as well as the I-MG molecules contract continuously and slowly as structure develops. A phenomenological model of Markovian evolution of the polymer chain undergoing folding, incorporating these features, has been developed, which fits well the experimentally observed time evolution of distance distributions. The observation that the "wrong turn" to the misfolded state has not been eliminated by evolution belies the common belief that the folding of functional protein sequences is very different from that of a random heteropolymer, and the former have been selected by evolution to fold quickly. (C) 2019 Elsevier Ltd. All rights reserved.
机译：为了妥善了解结构在蛋白质折叠反应过程中如何发展的洞察，有必要了解多肽链塌陷反应的性质和机制，这标志着折叠的启动。这里，时间分辨的荧光共振能量转移技术，其中使用时间荧光光强度的衰减来确定分子内距离分布的时间演变，已经利用研究小蛋白质，单胞素的折叠。可以看出，当折叠开始时，大约三分之一的蛋白质分子塌陷成熔融球液（I-Mg），从中通过连续进一步收缩来放松以转动到天然状态。较大的部分被困成亚稳定的错误折叠状态。从这种稳定状态的退出通过坍塌发生至下部自由能I-MG状态。由于激活能量障碍，此出口是秒的一段时间速度慢。随着结构的发展，捕获的错误分子以及I-Mg分子连续且缓慢地合同。已经开发出了经历折叠的聚合物链的马尔诺维亚演化的现象学模型，其掺入了这些特征，这适合实验观察到的距离分布的时间演变。观察到“错误转弯”到错误折叠状态尚未被进化所淘汰，呈现函数蛋白序列的折叠与随机杂化聚合物的折叠非常不同，并且前者通过进化选择快速折叠。 （c）2019 Elsevier Ltd.保留所有权利。

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