Comparative ultrafast spectroscopy and structural analysis of OCP1 and OCP2 from Tolypothrix
Comparative ultrafast spectroscopy and structural analysis of OCP1 and OCP2 from Tolypothrix
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DOI：
10.1016/j.bbabio.2019.148120
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发表时间：
2020-02-01
影响因子：
4.3
通讯作者：
Polivka, Tomas
中科院分区：
文献类型：
--
作者：
Kuznetsova, Valentyna;Dominguez-Martin, Maria Agustina;Polivka, Tomas
橙色类胡萝卜素蛋白(OCP)是一种结构和功能模块化的光活性蛋白，参与蓝藻的光保护。最近，基于生物信息学分析和系统发育关系，描述了OCP2和OCPx这两个新的OCP家族。OCP2的首次表征表明，与特性良好的OCP1相比，OCP2的光转化和反向转化速度更快，而藻胆体的荧光猝灭程度更低。此外，OCP2不受荧光恢复蛋白(FRP)的调节。在这项工作中，我们提出了一项结合超快光谱和结构分析的综合研究，以比较Tolypothrix PCC 7601的OCP1和OCP2的光激活机制。我们发现，尽管OCP1和OCP2的功能特征有显著差异，但它们的光谱性质是可比的。这表明OCP功能与结合的类胡萝卜素的光谱性质没有直接关系。此外，X射线足迹结构分析表明，OCP1和OCP2具有大致相同的光活化机制。然而，OCP2对辐射标记的反应较弱，这表明该蛋白不如OCP1灵活。这一观察结果可以解释OCP2的快速光转化。
The orange carotenoid protein (OCP) is a structurally and functionally modular photoactive protein involved in cyanobacterial photoprotection. Recently, based on bioinformatic analysis and phylogenetic relationships, new families of OCP have been described, OCP2 and OCPx. The first characterization of the OCP2 showed both faster photoconversion and back-conversion, and lower fluorescence quenching of phycobilisomes relative to the well-characterized OCP1. Moreover, OCP2 is not regulated by the fluorescence recovery protein (FRP). In this work, we present a comprehensive study combining ultrafast spectroscopy and structural analysis to compare the photoactivation mechanisms of OCP1 and OCP2 from Tolypothrix PCC 7601. We show that despite significant differences in their functional characteristics, the spectroscopic properties of OCP1 and OCP2 are comparable. This indicates that the OCP functionality is not directly related to the spectroscopic properties of the bound carotenoid. In addition, the structural analysis by X-ray footprinting reveals that, overall, OCP1 and OCP2 have grossly the same photoactivation mechanism. However, the OCP2 is less reactive to radiolytic labeling, suggesting that the protein is less flexible than OCP1. This observation could explain fast photoconversion of OCP2.