论文标题

瞬时红外光谱揭示的红色/绿色蓝细菌色素成染中的纳米秒蛋白动力学

Nanosecond protein dynamics in a red/green Cyanobacteriochrome revealed by transient IR spectroscopy

论文作者

Buhrke, David, Oppelt, Kerstin T., Heckmeier, Philipp J., Fernandez-Teran, Ricardo, Hamm, Peter

论文摘要

在过去的几十年中,使用生物物理方法对光感受体蛋白进行了广泛的研究,以获得对其工作机制的基本理解,并进一步指导从中开发光遗传学工具。时间分辨红外(IR)光谱是访问具有高时间分辨率的功能性非平衡过程的关键方法之一,但具有主要缺点,即实验数据通常非常复杂。将光谱响应与特定分子事件联系起来是一个主要障碍。在这里,我们研究了可见光和红外光谱区域中瞬时吸收光谱的组合方法的蓝细菌(CBCR)光感受器。我们通过两种不同的拟合方法分析(全局多拟合和寿命分析)在两个光谱区域中获得动力学信息。我们研究了在纳米卡和微秒时间示置的双稳定光循环(pr*和pg*)的两个方向上遵循光激发的基态动力学。我们发现两个与pr*衰减相关的基态中间体和pg*的衰减相关,并报告其互换的宏观时间常数。这些过程之一被分配给蛋白质主链的结构变化。在以后的延迟时间,光谱响应会随着时间的推移而延伸,这种效应可以通过终生分析更好地描述,而不是全球拟合。我们将其归因于蛋白质自由能景观的内在耐用性。

Over the last decades, photoreceptive proteins were extensively studied with biophysical methods to gain a fundamental understanding of their working mechanisms and further guide the development of optogenetic tools from them. Time-resolved infrared (IR) spectroscopy is one of the key methods to access their functional non-equilibrium processes with high temporal resolution, but has the major drawback that experimental data is usually highly complex. Linking the spectral response to specific molecular events is a major obstacle. Here, we investigate a cyanobacteriochrome (CBCR) photoreceptor with a combined approach of transient absorption spectroscopy in the Visible and IR spectral regions. We obtain kinetic information in both spectral regions by analysis with two different fitting methods, global multiexponential fitting and lifetime analysis. We investigate the ground state dynamics that follow photoexcitation in both directions of the bi-stable photocycle (Pr* and Pg*) in the nanosecond and microsecond time regime. We find two ground state intermediates associated with the decay of Pr* and four with Pg* and report the macroscopic time constants of their interconversions. One of these processes is assigned to a structural change in the protein backbone. At later delay times, the spectroscopic responses are stretched out in time, an effect that can be better described by the lifetime analysis than the global fit. We ascribe it to the intrinsic ruggedness of the free energy landscape of proteins.

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