The identification of CO₂-binding proteins is crucial to understanding CO₂-regulated molecular processes. CO₂ can form a reversible posttranslational modification through carbamylation of neutral N-terminal α-amino or lysine ε-amino groups. We have previously developed triethyloxonium (TEO) ion as a chemical proteomics tool for covalent trapping of carbamates, and here, we deploy TEO to identify ubiquitin as a mammalian CO₂-binding protein. We use ¹³C-NMR spectroscopy to demonstrate that CO₂ forms carbamates on the ubiquitin N terminus and ε-amino groups of lysines 6, 33, 48, and 63. We demonstrate that biologically relevant pCO₂ levels reduce ubiquitin conjugation at lysine-48 and down-regulate ubiquitin-dependent NF-κB pathway activation. Our results show that ubiquitin is a CO₂-binding protein and demonstrates carbamylation as a viable mechanism by which mammalian cells can respond to fluctuating pCO₂.

中文翻译：

---

泛素是一种二氧化碳结合蛋白

CO ₂结合蛋白的鉴定对于理解CO ₂调节的分子过程至关重要。CO ₂可以通过中性N-末端α-氨基或赖氨酸ε-氨基的氨甲酰化形成可逆的翻译后修饰。我们之前开发了三乙基氧 (TEO) 离子作为共价捕获氨基甲酸酯的化学蛋白质组学工具，在这里，我们部署 TEO 以将泛素鉴定为哺乳动物 CO ₂结合蛋白。我们使用¹³ C-NMR 光谱证明 CO ₂在泛素 N 末端和赖氨酸 6、33、48 和 63 的 ε-氨基上形成氨基甲酸酯。我们证明了生物学相关的p CO ₂水平降低 lysine-48 处的泛素结合并下调泛素依赖性 NF-κB 通路的激活。我们的研究结果表明，泛素是一种 CO ₂结合蛋白，并证明氨甲酰化是哺乳动物细胞可以对波动的p CO ₂作出反应的可行机制。