Color tuning in rhodopsins:: The mechanism for the spectral shift between bacteriorhodopsin and sensory rhodopsin II
Color tuning in rhodopsins:: The mechanism for the spectral shift between bacteriorhodopsin and sensory rhodopsin II
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DOI：
10.1021/ja062082i
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发表时间：
2006-08-23
影响因子：
15
通讯作者：
Elstner, Marcus
中科院分区：
文献类型：
--
作者：
Hoffmann, Michael;Wanko, Marius;Elstner, Marcus
通过比较光驱动质子泵细菌视紫红质（bR）和光探测器感觉视紫红质II（sRII）的光学性质，研究了视紫红质家族蛋白质的颜色调谐机制。尽管结构高度相似，但最大吸收从bR中的568 nm蓝移到sRII中的497 nm。这种转变的分子机制仍然是一个有争议的问题，它的澄清揭示了视网膜蛋白质颜色调节的一般机制。计算采用结合量子力学/分子力学（QM/MM）技术，使用DFT为基础的方法的基态性质和半经验OM 2/MRCI方法和从头算SORCI方法的激发态计算。该方法的高效率使我们能够研究包括动力学效应在内的各种方面。吸收位移以及各种突变实验和振动特性已被成功地再现。我们的研究结果表明，几个源有助于bR和sRII之间的光谱位移。主要因素是视网膜细胞外侧的互补区和结合口袋的氨基酸组成。我们的分析可以区分和识别的不同效果的细节，并导致一个清晰的画面的颜色调整的机制，这是在良好的协议与现有的实验数据。
The mechanism of color tuning in the rhodopsin family of proteins has been studied by comparing the optical properties of the light-driven proton pump bacteriorhodopsin (bR) and the light detector sensory rhodopsin II (sRII). Despite a high structural similarity, the maximal absorption is blue-shifted from 568 nm in bR to 497 nm in sRII. The molecular mechanism of this shift is still a matter of debate, and its clarification sheds light onto the general mechanisms of color tuning in retinal proteins. The calculations employ a combined quantum mechanical/molecular mechanical (QM/MM) technique, using a DFT-based method for ground state properties and the semiempirical OM2/MRCI method and ab initio SORCI method for excited state calculations. The high efficiency of the methodology has allowed us to study a wide variety of aspects including dynamical effects. The absorption shift as well as various mutation experiments and vibrational properties have been successfully reproduced. Our results indicate that several sources contribute to the spectral shift between bR and sRII. The main factors are the counterion region at the extracellular side of retinal and the amino acid composition of the binding pocket. Our analysis allows a distinction and identification of the different effects in detail and leads to a clear picture of the mechanism of color tuning, which is in good agreement with available experimental data.