FTIR study of the L intermediate of Anabaena sensory rhodopsin:: Structural changes in the cytoplasmic region
FTIR study of the L intermediate of Anabaena sensory rhodopsin:: Structural changes in the cytoplasmic region
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DOI：
10.1021/bi800941a
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发表时间：
2008-09-23
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：
Kawanabe, Akira;Furutani, Yuji;Kandori, Hideki
鱼腥藻感觉视紫质(ASR)是真细菌中发现的一种古生型视紫红质。编码ASR的基因与ASRT(ASR转导)形成一个操纵子，是一种14 kDa的可溶性蛋白质，这表明ASR通过激活可溶性转导而发挥光致变色传感器的功能。ASR的特征之一是M中间体的形成伴随着质子在细胞质一侧从Schiff碱转移到Asp217[ShiL，Yoon，S.R.，Bezerra，A.G.，Jr.，Jung，K.H.，and Brown，L.S.(2006)J.Mol]。比奥尔。358,686-700]，这与其他古生型视紫红质，如光驱动质子泵，细菌视紫红质(BR)形成了显著的对比。在本研究中，我们应用低温傅里叶变换红外光谱对170K下ASR的全反式进行了研究，并比较了L中间体和BR中间体的结构变化。ASR(L)减去ASR的差谱与BR的差谱基本相似，表明ASR和BR中的L态具有共同的结构。另一方面，在pH为5和7时，质子化羧酸在1722(+)和1703(-)cm(-1)处观察到独特的C=O伸缩带，并通过突变体将其归属于Glu36。Glu36位于细胞质一侧，与Schiff碱基的距离约为20埃。这一结果显示了ASR细胞质表面的结构变化(L)。对于水的拉伸振动，也观察到了依赖于pH的频率变化，这表明水分子参与了与Glu36和Asp217的氢键网络。我们将讨论ASR胞质区域中独特的氢键网络。
Anabaena sensory rhodopsin (ASR) is an archaeal-type rhodopsin found in eubacteria. The gene encoding ASR forms a single operon with ASRT (ASR transducer) that is a 14 kDa soluble protein, suggesting that ASR functions as a photochromic sensor by activating the soluble transducer. One of the characteristics of ASR is that the formation of the M intermediate accompanies a proton transfer from the Schiff base to Asp217 in the cytoplasmic side [Shi, L., Yoon, S. R., Bezerra, A. G., Jr., Jung, K. H., and Brown, L. S. (2006) J. Mol. Biol. 358, 686-700], in remarkable contrast to other archaeal-type rhodopsins such as a light-driven proton-pump, bacteriorhodopsin (BR). In this study, we applied low-temperature Fourier transform infrared (FTIR) spectroscopy to the all-trans form of ASR at 170 K, and compared the structural changes in the L intermediate with those of BR. The ASR(L) minus ASR difference spectra were essentially similar to those for BR, suggesting common structures for the L state in ASR and BR. On the other hand, unique C = O stretching bands of a protonated carboxylic acid were observed at 1722 (+) and 1703 (-) cm(-1) at pH 5 and 7, and assigned to Glu36 by use of mutants. Glu36 is located at the cytoplasmic side, and the distance from the Schiff base is about 20 angstrom. This result shows the structural changes at the cytoplasmic surface in ASR(L). pH-dependent frequency change was also observed for a water stretching vibration, suggesting that the water molecule is involved in a hydrogen-bonding network with Glu36 and Asp217. Unique hydrogen-bonding network in the cytoplasmic domain of ASR will be discussed.