Structural insights into blue-green light utilization by marine green algal light harvesting complex II at 2.78 ?
Structural insights into blue-green light utilization by marine green algal light harvesting complex II at 2.78 ?
复制标题
海洋绿藻光捕获复合物 II 在 2.78 时对蓝绿光利用的结构见解？
DOI：
10.1016/j.bbadva.2022.100064
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Fujii Ritsuko
中科院分区：
文献类型：
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作者：
Seki Soichiro;Nakaniwa Tetsuko;Castro-Hartmann Pablo;Sader Kasim;Kawamoto Akihiro;Tanaka Hideaki;Qian Pu;Kurisu Genji;Fujii Ritsuko
存在于植物和绿色藻类中的捕光复合物II（LHCII）吸收太阳能以促进光化学反应。一种海洋绿色大型浮游植物，松藻，表现出独特的特性，吸收蓝绿色光从太阳在光化学反应，而在水下，由于存在色素改变LHCII称为管黄质叶绿素/b结合蛋白（SCP）。在这项研究中，我们确定了SCP的结构，分辨率为2.78毫米，使用低温电子显微镜。SCP具有三聚体结构，其中植物型LHCII中每个含有两个叶黄素和两个叶绿素分子的单体分别被管黄质及其酯和两个叶绿素b分子取代。管黄质占据SCP中的结合位点，该SCP在三聚体内核中具有极性，并表现出扭曲的共轭链，该链包含与脱辅基蛋白的半胱氨酸残基氢键合的羰基。这些特征表明，管黄质分子负责SCP的特征绿色吸收。被取代的叶绿素b分子延伸了基质侧叶绿素b簇的区域，跨越两个相邻的单体。
Light-harvesting complex II (LHCII) present in plants and green algae absorbs solar energy to promote photochemical reactions. A marine green macroalga,Codium fragile, exhibits the unique characteristic of absorbing blue-green light from the sun during photochemical reactions while being underwater owing to the presence of pigment-altered LHCII called siphonaxanthin–chlorophylla/b-binding protein (SCP). In this study, we determined the structure of SCP at a resolution of 2.78 Å using cryogenic electron microscopy. SCP has a trimeric structure, wherein each monomer containing two lutein and two chlorophyllamolecules in the plant-type LHCII are replaced by siphonaxanthin and its ester and two chlorophyllbmolecules, respectively. Siphonaxanthin occupies the binding site in SCP having a polarity in the trimeric inner core, and exhibits a distorted conjugated chain comprising a carbonyl group hydrogen bonded to a cysteine residue of apoprotein. These features suggest that the siphonaxanthin molecule is responsible for the characteristic green absorption of SCP. The replaced chlorophyllbmolecules extend the region of the stromal side chlorophyllbcluster, spanning two adjacent monomers.