Photoisomerization and proton transfer in photoactive yellow protein.
Photoisomerization and proton transfer in photoactive yellow protein.
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DOI：
10.1021/ja0294461
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发表时间：
2003-06
影响因子：
15
通讯作者：
M. J. Thompson;D. Bashford;Louis Noodleman;E. Getzoff
中科院分区：
文献类型：
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作者：
M. J. Thompson;D. Bashford;Louis Noodleman;E. Getzoff
光敏黄蛋白（PYP）是一种细菌光传感器，含有一个对香豆酰硫酯发色团，吸收蓝光，启动涉及一系列构象变化的光循环。在这里，我们提出了计算研究，以解决有关原子结构和光谱测量早期光循环中间体之间的对应关系的不确定性和争议。用含时密度泛函理论（TDDFT）研究PYP光循环的初始纳秒，计算发色团光致异构化和质子转移的能量分布，并计算激发能以确定光循环中间体.计算的势能面光异构化匹配的关键，实验确定的光谱参数。Genick等人[Genick，U. K.的; Soltis，S. M.; Kuhn，P.;卡内斯特雷利岛L.的; Getzoff，E. D. Nature 1998，392，206-209]支持其归属为PYP（B）（I（0））中间体。PYP（B）中间体的时间分辨室温（298 K）光谱与其低温（77 K）吸光度之间的差异归因于前者中主要是去质子化的发色团，而后者中主要是质子化的发色团。这与普遍认为发色团质子化直到PYP（L）（I（1）或pR）中间体之后才发生的观点形成对比。计算确定了PYP（L）中间体中发色团的结构，并显示出去质子化，与实验一致。基于我们的PYP（B）和PYP（L）模型的计算导致了对PYP（BL）中间体的认识，仅在低温下观察到。结果表明，质子是更移动的之间的谷氨酸46和发色团比以前实现。这里提出的研究结果提供了一个例子的见解，理论研究可以有助于实验结构和光谱的统一分析。
The photoactive yellow protein (PYP) is a bacterial photosensor containing a para-coumaryl thioester chromophore that absorbs blue light, initiating a photocycle involving a series of conformational changes. Here, we present computational studies to resolve uncertainties and controversies concerning the correspondence between atomic structures and spectroscopic measurements on early photocycle intermediates. The initial nanoseconds of the PYP photocycle are examined using time-dependent density functional theory (TDDFT) to calculate the energy profiles for chromophore photoisomerization and proton transfer, and to calculate excitation energies to identify photocycle intermediates. The calculated potential energy surface for photoisomerization matches key, experimentally determined, spectral parameters. The calculated excitation energy of the photocycle intermediate cryogenically trapped in a crystal structure by Genick et al. [Genick, U. K.; Soltis, S. M.; Kuhn, P.; Canestrelli, I. L.; Getzoff, E. D. Nature 1998, 392, 206-209] supports its assignment to the PYP(B) (I(0)) intermediate. Differences between the time-resolved room temperature (298 K) spectrum of the PYP(B) intermediate and its low temperature (77 K) absorbance are attributed to a predominantly deprotonated chromophore in the former and protonated chromophore in the latter. This contrasts with the widely held belief that chromophore protonation does not occur until after the PYP(L) (I(1) or pR) intermediate. The structure of the chromophore in the PYP(L) intermediate is determined computationally and shown to be deprotonated, in agreement with experiment. Calculations based on our PYP(B) and PYP(L) models lead to insights concerning the PYP(BL) intermediate, observed only at low temperature. The results suggest that the proton is more mobile between Glu46 and the chromophore than previously realized. The findings presented here provide an example of the insights that theoretical studies can contribute to a unified analysis of experimental structures and spectra.