Assignment of the hydrogen-out-of-plane and -in-plane vibrations of the retinal chromophore in the K intermediate of pharaonis phoborhodopsin
Assignment of the hydrogen-out-of-plane and -in-plane vibrations of the retinal chromophore in the K intermediate of pharaonis phoborhodopsin
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DOI：
10.1021/bi0610597
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发表时间：
2006-10-03
期刊：
影响因子：
2.9
通讯作者：
Kandori, Hideki
中科院分区：
文献类型：
--
作者：
Furutani, Yuji;Sudo, Yuki;Kandori, Hideki
pharaonis phoborhodopsin（ppR;也称为法老感觉视紫红质II（pharaonissensorrhodopsin II，psR-II）是法老嗜盐碱单胞菌中负趋光性的光感受器蛋白。视网膜发色团从全反式到13-顺式的光异构化引发蛋白质的构象变化，导致同源转导蛋白（pHtrII）的激活。阐明初始光反应，形成的K中间体的ppR，是重要的理解的光子能量的存储机制。我们已经报道了K-ppR傅里叶变换红外（FTIR）光谱，包括几个振动带的视网膜，蛋白质，和内部水分子。有趣的是，在氢平面外（HOOP）区域观察到的振动带比光驱动质子泵细菌视紫红质更多。这一结果表明，在初始中间体形成后，ppR结合口袋中的视黄色素团的空间限制分布更广。在这项研究中，我们分配的HOOP和氢的面内振动的低温FTIR光谱应用于ppR重建与视网膜氘在C7，C8，C10-C12，C14，和C15。结果表明，966（+）/971（-）和958（+）/961（-）cm（-1）谱带分别归属于C7=C8和C11=C12 Au HOOP模式，表明结构变化扩展到视网膜的中部。在1001、994、987和979 cm（-1）处的正带归属于K中间体的C15-HOOP振动，其频率与135 K下捕获的细菌视紫红质的K-L中间体的频率相似。在864 cm（-1）处的另一个阳性带被指定为C14-HOOP振动。相对较多的氢平面振动正带也支持视网膜结构变化的广泛分布。这些结果表明，光能量主要储存在Schiff碱区周围的畸变，而一部分能量转移到视网膜的远端部分。
pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, psR-II) is a photoreceptor protein for negative phototaxis in Natronomonas pharaonis. Photoisomerization of the retinal chromophore from all-trans to 13-cis initiates conformational changes of the protein leading to activation of the cognate transducer protein (pHtrII). Elucidation of the initial photoreaction, formation of the K intermediate of ppR, is important for understanding the mechanism of storage of photon energy. We have reported the K minus ppR Fourier transform infrared ( FTIR) spectra, including several vibrational bands of the retinal, the protein, and internal water molecules. It is interesting that more vibrational bands were observed in the hydrogen-out-of-plane ( HOOP) region than for the light-driven proton pump, bacteriorhodopsin. This result implied that the steric constraints on the retinal chromophore in the binding pocket of ppR are distributed more widely upon formation of the initial intermediate. In this study, we assigned the HOOP and hydrogen-in-plane vibrations by means of low-temperature FTIR spectroscopy applied to ppR reconstituted with retinal deuterated at C7, C8, C10-C12, C14, and C15. As a result, the 966 (+)/971 (-) and 958 (+)/961 (-) cm(-1) bands were assigned to the C7=C8 and C11=C12 Au HOOP modes, respectively, suggesting that the structural changes spread to the middle part of the retinal. The positive bands at 1001, 994, 987, and 979 cm(-1) were assigned to the C15-HOOP vibrations of the K intermediate, whose frequencies are similar to those of the K-L intermediate of bacteriorhodopsin trapped at 135 K. Another positive band at 864 cm(-1) was assigned to the C14-HOOP vibration. Relatively many positive bands of hydrogen-in-plane vibrations supported the wide distribution of structural changes of the retinal as well. These results imply that the light energy was stored mainly in the distortions around the Schiff base region while some part of the energy was transferred to the distal part of the retinal.