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Fast events in protein folding initiated by nanosecond laser photolysis.

机译:纳秒级激光光解引发的蛋白质折叠中的快速事件。

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摘要

Initiation of protein folding by light can dramatically improve the time resolution of kinetic studies. Here we present an example of an optically triggered folding reaction by using nanosecond photodissociation of the heme-carbon monoxide complex of reduced cytochrome c. The optical trigger is based on the observation that under destabilizing conditions cytochrome c can be unfolded by preferential binding of carbon monoxide to the covalently attached heme group in the unfolded state. Photodissociation of the carbon monoxide thus triggers the folding reaction. We used time-resolved absorption spectroscopy to monitor binding at the heme. Before folding begins we observe transient binding of both nonnative and native ligands from the unfolded polypeptide on a microsecond time scale. Kinetic modeling suggests that the intramolecular binding of methionine-65 and -80 is faster than that of histidine-26 and -33, even though the histidines are closer to the heme. This optical trigger should provide a powerful method for studying chain collapse and secondary structure formation in cytochrome c without any limitations in time resolution.
机译:通过光引发蛋白质折叠可以显着提高动力学研究的时间分辨率。在这里,我们介绍了使用还原的细胞色素c的血红素-一氧化碳复合物进行纳秒光解离的光学触发折叠反应的示例。光学触发是基于以下观察:在不稳定条件下,细胞色素c可以通过一氧化碳与未折叠状态的共价连接的血红素基团的优先结合而展开。一氧化碳的光解离因此触发了折叠反应。我们使用时间分辨吸收光谱法监测血红素上的结合。在折叠开始之前,我们在微秒时间内观察到来自未折叠多肽的非天然和天然配体的瞬时结合。动力学建模表明,即使组氨酸更靠近血红素,蛋氨酸-65和-80的分子内结合也比组氨酸-26和-33的分子内结合更快。该光触发应提供一种强大的方法来研究细胞色素c中的链折叠和二级结构形成,而不受时间分辨率的限制。

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