Abstract：
In cyanobacteria, Elongation factor Tu (EF-Tu) plays a crucial role in the repair of photosystem II (PSII), which is highly susceptible to oxidative stress induced by light exposure and regulated by reactive oxygen species (ROS). However, the specific molecular mechanism governing the functional regulation of EF-Tu by ROS remains unclear. Previous research has shown that a mutated EF-Tu, where C82 is substituted with a Ser residue, can alleviate photoinhibition, highlighting the important role of C82 in EF-Tu photosensitivity. In this study, we elucidated how ROS deactivate EF-Tu by examining the crystal structures of EF-Tu in both wild-type and mutated form (C82S) individually at resolutions of 1.7 Å and 2.0 Å in Synechococcus elongatus PCC 7942 complexed with GDP. Specifically, the GDP-bound form of EF-Tu adopts an open conformation with C82 located internally, making it resistant to oxidation. Coordinated conformational changes in switches I and II create a tunnel that positions C82 for ROS interaction, revealing the vulnerability of the closed conformation of EF-Tu to oxidation. An analysis of these two structures reveals that the precise spatial arrangement of C82 plays a crucial role in modulating EF-Tu\'s response to ROS, serving as a regulatory element that governs photosynthetic biosynthesis.
摘要：
在蓝细菌中，延长因子Tu（EF-Tu）在光系统II（PSII）的修复中起着至关重要的作用，它非常容易受到光暴露引起的氧化应激和活性氧（ROS）的调节。然而,目前尚不清楚ROS调控EF-Tu功能的具体分子机制。先前的研究表明，突变的EF-Tu，其中C82被Ser残基取代，可以减轻光抑制，强调了C82在EF-Tu光敏中的重要作用。在这项研究中,我们阐明了ROS如何通过分别检查野生型和突变形式（C82S）的EF-Tu的晶体结构来使EF-Tu失活，分辨率分别为1.7和2.0。具体来说,EF-Tu的GDP约束形式采用开放式构型，C82位于内部，使其抗氧化。开关I和II的协调构象变化创建了一个通道，将C82定位为ROS相互作用，揭示了EF-Tu封闭构象对氧化的脆弱性。对这两种结构的分析表明，C82的精确空间排列在调节EF-Tu对ROS的反应中起着至关重要的作用。作为控制光合生物合成的调节元件。
