Groot Marie Louise, van Wilderen Luuk J G W, Larsen Delmar S, van der Horst Michael A, van Stokkum Ivo H M, Hellingwerf Klaas J, van Grondelle Rienk
Faculty of Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
Biochemistry. 2003 Sep 2;42(34):10054-9. doi: 10.1021/bi034878p.
Photoactive yellow protein (PYP) is a bacterial blue light sensor that induces Halorhodospira halophila to swim away from intense blue light. Light absorption by PYP's intrinsic chromophore, p-coumaric acid, leads to the initiation of a photocycle that comprises several distinct intermediates. Here we describe the initial structural changes of the chromophore and its nearby amino acids, using visible pump/mid-infrared probe spectroscopy. Upon photoexcitation, the trans bands of the chromophore are bleached, and shifts of the phenol ring bands occur. The latter are ascribed to charge translocation, which probably plays an essential role in driving the trans to cis isomerization process. We conclude that breaking of the hydrogen bond of the chromophore's C=O group with amino acid Cys69 and formation of a stable cis ground state occur in approximately 2 ps. Dynamic changes also include rearrangements of the hydrogen-bonding network of the amino acids around the chromophore. Relaxation of the coumaryl tail of the chromophore occurs in 0.9-1 ns, which event we identify with the I(0) to I(1) transition observed in visible spectroscopy.
光活性黄色蛋白（PYP）是一种细菌蓝光传感器，可诱导嗜盐嗜盐红螺菌游离强光。PYP的固有发色团对香豆酸吸收光后，引发一个包含几种不同中间体的光循环。在此，我们使用可见泵浦/中红外探测光谱法描述了发色团及其附近氨基酸的初始结构变化。光激发后，发色团的反式谱带被漂白，酚环谱带发生位移。后者归因于电荷转移，这可能在驱动反式到顺式异构化过程中起关键作用。我们得出结论，发色团C=O基团与氨基酸Cys69之间的氢键断裂以及稳定顺式基态的形成大约在2皮秒内发生。动态变化还包括发色团周围氨基酸氢键网络的重排。发色团香豆酰尾部的弛豫在0.9 - 1纳秒内发生，我们将此事件与可见光谱中观察到的I(0)到I(1)跃迁联系起来。
