Photoprotective sites in the violaxanthin-chlorophyll α binding Protein (VCP) from Nannochloropsis gaditana
Photoprotective sites in the violaxanthin-chlorophyll α binding Protein (VCP) from Nannochloropsis gaditana
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DOI：
10.1016/j.bbabio.2014.03.014
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发表时间：
2014-08-01
影响因子：
4.3
通讯作者：
Morosinotto, Tomas
中科院分区：
文献类型：
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作者：
Carbonera, Donatella;Agostini, Alessandro;Morosinotto, Tomas
紫黄质-叶绿素a结合蛋白（Violaxanthin-chlorophylla binding protein，VCP）是海洋微绿球藻（Nannochloropsis gaditana）的主要捕光复合物（light harvesting complex，LHC）。它结合叶绿素a、紫黄质和紫黄质，后者以19'癸酸酯/辛酸酯的形式。属于这一组的藻类的光合作用装置在过去已经很差的特点，但他们现在收到越来越多的兴趣，也因为他们可能的生物技术应用在生物燃料生产。在这项工作中，分离的VCP蛋白已被研究通过先进的EPR技术，以证明存在的光保护机制的基础上的三重态-三重态能量转移（TTET），叶绿素和类胡萝卜素分子之间发生。这个过程已经在属于各种光合生物的几种捕光复合体中观察到。我们使用光学检测磁共振（ODMR）来识别由光激发填充的三重态，并描述携带三重态的发色团的光学性质。与此同时，时间分辨EPR（TR-EPR）和脉冲EPR已被用来深入了解TTET机制，揭示参与光保护的色素位点的结构特征。光谱数据的分析表明，VCP，硅藻的FCP和LHC-Ⅱ从高等植物之间有很强的相似性。虽然这些天线蛋白有不同的序列和绑定不同的色素，结果表明，在所有成员的LHC超家族有一个保守的结构组织的蛋白质核心，由两个中央类胡萝卜素包围的5个叶绿素a分子，这起着基本的光保护作用，通过类胡萝卜素三联体形成叶绿素三联体淬灭。(C)2014爱思唯尔有限公司版权所有。
Violaxanthin-chlorophyll a binding protein (VCP) is the major light harvesting complex (LHC) of the Heterokonta Nannochloropsis gaditana. It binds chlorophyll a, violaxanthin and vaucheriaxanthin, the last in the form of 19' deca/octanoate esters. Photosynthetic apparatus of algae belonging to this group have been poorly characterized in the past, but they are now receiving an increasing interest also because of their possible biotechnological application in biofuel production. In this work, isolated VCP proteins have been studied by means of advanced EPR techniques in order to prove the presence of the photoprotective mechanism based on the triplet-triplet energy transfer (TTET), occurring between chlorophyll and carotenoid molecules. This process has been observed before in several light harvesting complexes belonging to various photosynthetic organisms. We used Optically Detected Magnetic Resonance (ODMR) to identify the triplet states populated by photoexcitation, and describe the optical properties of the chromophores carrying the triplet states. In parallel, time-resolved EPR (TR-EPR) and pulse EPR have been employed to get insight into the TTET mechanism and reveal the structural features of the pigment sites involved in photoprotection. The analysis of the spectroscopic data shows a strong similarity among VCP, FCP from diatoms and LHC-II from higher plants. Although these antenna proteins have differentiated sequences and bind different pigments, results suggest that in all members of the LHC superfamily there is a protein core with a conserved structural organization, represented by two central carotenoids surrounded by five chlorophyll a molecules, which plays a fundamental photoprotective role in Chl triplet quenching through carotenoid triplet formation. (C) 2014 Elsevier B.V. All rights reserved.