Structure of the antenna complex expressed during far-red light photoacclimation in Synechococcus sp. PCC 7335.
Structure of the antenna complex expressed during far-red light photoacclimation in Synechococcus sp. PCC 7335.
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DOI：
10.1016/j.jbc.2023.105590
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发表时间：
2024-02
影响因子：
4.8
通讯作者：
Bryant, Donald A
中科院分区：
文献类型：
--
作者：
Gisriel, Christopher J;Shen, Gaozhong;Brudvig, Gary W;Bryant, Donald A
远红光光驯化（FaRLiP）是一些蓝藻表现出的兼性反应，使它们能够吸收和利用较低能量的光（700-800 nm），而不是通常用于氧光合作用的波长（400-700 nm）。在这个过程中，光合装置的三个基本组成部分发生了变化：光系统I、光系统II和藻胆体。在这三种情况下，至少在这些色素-蛋白质复合物中发现的一些发色团被相对于在可见光下产生的类似复合物具有红移吸光度的发色团所取代。最近的结构和光谱研究已经阐明了这两种光系统在吸收和利用远红光时的重要特征，但对FaRLiP过程中产生的修饰藻胆蛋白知之甚少。我们使用单颗粒低温电镜（cro - em）测定了海洋蓝细菌聚藻球菌（Synechococcus sp. PCC 7335）在FaRLiP过程中吸收远红光的藻脂蛋白核心复合物的分子结构。该结构揭示了许多红移异体藻蓝蛋白变体的排列以及作为该复合体末端发射体的发色团的可能位置。它还表明能量是如何转移到FaRLiP过程中产生的光系统II复合体的。该结构还可以与其他先前研究过的异藻蓝蛋白进行比较，以深入了解藻蓝胆素发色团是如何调节以吸收远红光的。这些研究为FaRLiP（一种广泛存在的蓝藻光驯化机制）期间远红光的收获和利用提供了新的见解。
Far-red light photoacclimation, or FaRLiP, is a facultative response exhibited by some cyanobacteria that allows them to absorb and utilize lower energy light (700–800 nm) than the wavelengths typically used for oxygenic photosynthesis (400–700 nm). During this process, three essential components of the photosynthetic apparatus are altered: photosystem I, photosystem II, and the phycobilisome. In all three cases, at least some of the chromophores found in these pigment–protein complexes are replaced by chromophores that have red-shifted absorbance relative to the analogous complexes produced in visible light. Recent structural and spectroscopic studies have elucidated important features of the two photosystems when altered to absorb and utilize far-red light, but much less is understood about the modified phycobiliproteins made during FaRLiP. We used single-particle, cryo-EM to determine the molecular structure of a phycobiliprotein core complex comprising allophycocyanin variants that absorb far-red light during FaRLiP in the marine cyanobacterium Synechococcus sp. PCC 7335. The structure reveals the arrangement of the numerous red-shifted allophycocyanin variants and the probable locations of the chromophores that serve as the terminal emitters in this complex. It also suggests how energy is transferred to the photosystem II complexes produced during FaRLiP. The structure additionally allows comparisons with other previously studied allophycocyanins to gain insights into how phycocyanobilin chromophores can be tuned to absorb far-red light. These studies provide new insights into how far-red light is harvested and utilized during FaRLiP, a widespread cyanobacterial photoacclimation mechanism.