Echinenone vibrational properties: From solvents to the orange carotenoid protein
Echinenone vibrational properties: From solvents to the orange carotenoid protein
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DOI：
10.1016/j.bbabio.2015.05.010
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发表时间：
2015-10-01
影响因子：
4.3
通讯作者：
Robert, Bruno
中科院分区：
文献类型：
--
作者：
Kish, Elizabeth;Pinto, Maria Manuela Mendes;Robert, Bruno
橙类胡萝卜素蛋白（OCP）是一种结合紫锥烯酮作为发色团的蓝藻光活性蛋白；它参与了这些光合生物对抗强光照的光保护。在静息状态下，OCP呈现橙色（OCPo），当暴露在蓝绿色光下时变为红色（OCPr）。本文将共振拉曼光谱和分子模型相结合，研究了不同形式OCP的电子吸收特性的机制。我们的研究结果表明，OCPo中至少存在两种类胡萝卜素构型，这表明OCPo具有相当的灵活性，并且OCPo到OCPr的转变必须涉及到结合的棘烯酮的表观共轭长度的增加。共振拉曼表明该发色团在OCPo中必须处于全反式结构。密度泛函理论（DFT）计算与两种OCP形式的拉曼光谱结果一致，表明OCPo到OCPr的转变必然涉及到烯醌s顺式到s反式的异构化，这会影响其共轭端链环的位置，或者烯醌环的弯曲会使它们从OCPo形式的C=C共轭平面进入OCPr形式的C=C平面。(C) 2015 Elsevier B.V.版权所有
Orange carotenoid protein (OCP) is a cyanobacterial photoactive protein which binds echinenone as a chromophore; it is involved in photoprotection of these photosynthetic organisms against intense illumination. In its resting state, OCP appears orange (OCPo), and turns into a red form (OCPr) when exposed to blue-green light. Here we have combined resonance Raman spectroscopy and molecular modeling to investigate the mechanisms underlying the electronic absorption properties of the different forms of OCP. Our results show that there are at least two carotenoid configurations in the OCPo, suggesting that it is quite flexible, and that the OCPo to OCPr transition must involve an increase of the apparent conjugation length of the bound echinenone. Resonance Raman indicates that this chromophore must be in an all-trans configuration in OCPo. Density functional theory (DFT) calculations, in agreement with the Raman spectra of both OCP forms, show that the OCPo to OCPr transition must involve either an echinenone s-cis to s-trans isomerization which would affect the position of its conjugated end-chain rings, or a bending of the echinenone rings which would bring them from out of the plane of the C=C conjugated plane in the OCPo form into the C=C plane in the OCPr form. (C) 2015 Elsevier B.V. All rights reserved.