Department of Gastroenterology of Ruijin Hospital, Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
EMBO J. 2023 Jul 3;42(13):e112333. doi: 10.15252/embj.2022112333. Epub 2023 May 15.
Enteric bacteria use up to 15% of their cellular energy for ammonium assimilation via glutamine synthetase (GS)/glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) in response to varying ammonium availability. However, the sensory mechanisms for effective and appropriate coordination between carbon metabolism and ammonium assimilation have not been fully elucidated. Here, we report that in Salmonella enterica, carbon metabolism coordinates the activities of GS/GDH via functionally reversible protein lysine acetylation. Glucose promotes Pat acetyltransferase-mediated acetylation and activation of adenylylated GS. Simultaneously, glucose induces GDH acetylation to inactivate the enzyme by impeding its catalytic centre, which is reversed upon GDH deacetylation by deacetylase CobB. Molecular dynamics (MD) simulations indicate that adenylylation is required for acetylation-dependent activation of GS. We show that acetylation and deacetylation occur within minutes of "glucose shock" to promptly adapt to ammonium/carbon variation and finely balance glutamine/glutamate synthesis. Finally, in a mouse infection model, reduced S. enterica growth caused by the expression of adenylylation-mimetic GS is rescued by acetylation-mimicking mutations. Thus, glucose-driven acetylation integrates signals from ammonium assimilation and carbon metabolism to fine-tune bacterial growth control.
肠细菌通过谷氨酰胺合成酶（GS）/谷氨酸合酶（GOGAT）和谷氨酸脱氢酶（GDH）将其细胞能量的 15%用于铵同化，以响应不同的铵可用性。然而，对于碳代谢和铵同化之间的有效和适当协调的感应机制尚未完全阐明。在这里，我们报告在沙门氏菌中，碳代谢通过功能可逆的蛋白赖氨酸乙酰化来协调 GS/GDH 的活性。葡萄糖促进 Pat 乙酰转移酶介导的腺苷酰化和活化的 GS。同时，葡萄糖诱导 GDH 乙酰化，通过阻碍其催化中心来使酶失活，而 CobB 通过去乙酰化使 GDH 去乙酰化可逆转该过程。分子动力学（MD）模拟表明，腺苷酰化是 GS 依赖于乙酰化的激活所必需的。我们表明，在“葡萄糖冲击”后的几分钟内就会发生乙酰化和去乙酰化，从而迅速适应铵/碳的变化，并精细平衡谷氨酰胺/谷氨酸的合成。最后，在小鼠感染模型中，通过表达腺苷酰化模拟 GS 引起的 S. enterica 生长减少可通过乙酰化模拟突变得到挽救。因此，葡萄糖驱动的乙酰化整合了来自铵同化和碳代谢的信号，以微调细菌生长控制。
