YdiU regulates Salmonella oxidation balance by UMPylation of SodA

YdiU is a novel UMPylation modification enzyme that plays an important role in regulating chaperones, flagellar synthesis, and iron absorption in Salmonella. Here, we report that YdiU plays an important role in regulating oxidative stress in Salmonella. The expression of ydiU was dramatically induced by hydrogen peroxide (H2O2) and the survivability of △ydiU was significantly stronger than that of WT under oxidative stress. Interestingly, in vitro and in vivo experiments showed that YdiU can interact with SodA and UMPylate it only in the presence of H2O2. Further study showed slight changes in the secondary structure of SodA under oxidative stress. Structural analysis of native protein and H2O2-treated protein showed that H2O2 treatment affected the conformation of Met24. The modification site Tyr12 is near Met24, and Tyr12 exposure may facilitate UMPylation by YdiU after H2O2 treatment. In addition, in vivo and in vitro experiments showed that YdiU negatively regulates SodA activity. Therefore, our results identify new biological functions of YdiU, highlight the importance of UMPylation in bacterial oxidation balance, and provide the theoretical basis to study Salmonella survival and pathogenesis.YdiU是一种新型尿苷单磷酸化（UMPylation）修饰酶，在沙门氏菌中对分子伴侣、鞭毛合成及铁吸收过程发挥关键调控作用。本研究报道了YdiU在沙门氏菌氧化应激调控中的重要功能。研究发现，ydiU的表达可被过氧化氢（H₂O₂）显著诱导；且在氧化应激条件下，△ydiU缺失株的存活率显著高于野生型（WT）菌株。有趣的是，体外与体内实验均证实，仅在过氧化氢存在的前提下，YdiU方可与SodA相互作用并对其进行尿苷单磷酸化修饰。进一步研究显示，氧化应激条件下SodA的二级结构仅发生轻微改变。对天然蛋白与过氧化氢处理后的蛋白进行结构分析显示，过氧化氢处理会影响Met24的构象。修饰位点Tyr12紧邻Met24，过氧化氢处理后Tyr12的暴露或可促进YdiU介导的尿苷单磷酸化修饰。此外，体内外实验均证实YdiU对SodA活性具有负调控作用。综上，本研究揭示了YdiU全新的生物学功能，凸显了尿苷单磷酸化修饰在细菌氧化平衡中的重要性，为沙门氏菌的存活机制与致病机制研究提供了理论依据。