Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Branišovská 31, 370 05, České Budějovice, Czech Republic.
Commun Biol. 2024 Oct 29;7(1):1406. doi: 10.1038/s42003-024-07101-9.
Photosynthetic organisms harvest light for energy. Some eukaryotic algae have specialized in harvesting far-red light by tuning chlorophyll a absorption through a mechanism still to be elucidated. Here, we combined optically detected magnetic resonance and pulsed electron paramagnetic resonance measurements on red-adapted light-harvesting complexes, rVCP, isolated from the freshwater eustigmatophyte alga Trachydiscus minutus to identify the location of the pigments responsible for this remarkable adaptation. The pigments have been found to belong to an excitonic cluster of chlorophylls a at the core of the complex, close to the central carotenoids in L1/L2 sites. A pair of structural features of the Chl a403/a603 binding site, namely the histidine-to-asparagine substitution in the magnesium-ligation residue and the small size of the amino acid at the i-4 position, resulting in a [A/G]xxxN motif, are proposed to be the origin of this trait. Phylogenetic analysis of various eukaryotic red antennae identified several potential LHCs that could share this tuning mechanism. This knowledge of the red light acclimation mechanism in algae is a step towards rational design of algal strains in order to enhance light capture and efficiency in large-scale biotechnology applications.
光合生物利用光能获取能量。一些真核藻类通过一种尚未阐明的机制专门用于收集远红光，通过调整叶绿素 a 的吸收来实现。在这里，我们结合了来自淡水等鞭金藻 Trachydiscus minutus 的红光收集复合物 rVCP 的光探测磁共振和脉冲电子顺磁共振测量，以确定负责这种显著适应的色素的位置。这些色素被发现属于该复合物核心处的叶绿素 a 的激子簇，靠近 L1/L2 位置的中心类胡萝卜素。Chl a403/a603 结合位点的一对结构特征，即镁配位残基中的组氨酸到天冬酰胺取代和 i-4 位氨基酸的小尺寸，导致 [A/G]xxxN 基序，被认为是这种特征的起源。对各种真核红光天线的系统发育分析鉴定了几个可能共享这种调谐机制的潜在 LHC。对藻类中红光适应机制的了解是朝着理性设计藻类菌株以提高大规模生物技术应用中的光捕获和效率迈出的一步。
