S-Nitrosothiols (RSNOs) represent an important class of post-translational modifications that preserve and amplify the actions of nitric oxide and regulate enzyme activity. Several regulatory proteins are now verified targets of cellular S-nitrosation, and the direct detection of S-nitrosated residues in proteins has become essential to better understand RSNO-mediated signaling. Current RSNO detection depends on indirect assays that limit their overall specificity and reliability. Herein, we report the reaction of S-nitrosated cysteine, glutathione, and a mutated C165S alkyl hydroperoxide reductase with the water-soluble phosphine tris(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt hydrate (TXPTS). A combination of NMR and MS techniques reveals that these reactions produce covalent S-alkylphosphonium ion adducts (with S−P⁺ connectivity), TXPTS oxide, and a TXPTS-derived aza-ylide. Mechanistically, this reaction may proceed through an S-substituted aza-ylide or the direct displacement of nitroxyl from the RSNO group. This work provides a new means for detecting and quantifying S-nitrosated species in solution and suggests that phosphines may be useful tools for understanding the complex physiological roles of S-nitrosation and its implications in cell signaling and homeostasis.

中文翻译：

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水溶性三芳基膦作为蛋白质 S-亚硝化的生物标志物

S-亚硝基硫醇 (RSNO) 代表一类重要的翻译后修饰，可保留和放大一氧化氮的作用并调节酶活性。几种调节蛋白现已成为细胞S-亚硝化的验证靶标，直接检测蛋白质中的S-亚硝化残基对于更好地了解 RSNO 介导的信号传导变得至关重要。目前的 RSNO 检测依赖于限制其整体特异性和可靠性的间接检测。在这里，我们报告了S的反应-亚硝化半胱氨酸、谷胱甘肽和突变的 C165S 烷基氢过氧化物还原酶与水溶性膦三（4,6-二甲基-3-磺基苯基）膦三钠盐水合物 (TXPTS)。NMR 和 MS 技术的结合表明，这些反应会产生共价S-烷基鏻离子加合物（具有 S-P ⁺连接性）、TXPTS 氧化物和 TXPTS 衍生的氮杂叶立德。从机制上讲，该反应可以通过S-取代的氮杂-叶立德或从 RSNO 基团直接置换硝酰基来进行。这项工作提供了一种检测和量化溶液中S-亚硝化物质的新方法，并表明膦可能是了解S的复杂生理作用的有用工具-亚硝化及其在细胞信号传导和体内平衡中的影响。