Department of Microbiology and Immunology, Stritch School of Medicine, Health Sciences Division, Loyola University Chicagogrid.164971.c, Maywood, Illinois, USA.
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaigngrid.35403.31, Urbana, Illinois, USA.
mBio. 2022 Jun 28;13(3):e0122422. doi: 10.1128/mbio.01224-22. Epub 2022 May 23.
ε-lysine acetylation is a common posttranslational modification observed in diverse species of bacteria. Aside from a few central metabolic enzymes and transcription factors, little is known about how this posttranslational modification regulates protein activity. In this work, we investigated how lysine acetylation affects translation in Escherichia coli. In multiple species of bacteria, ribosomal proteins are highly acetylated at conserved lysine residues, suggesting that this modification may regulate translation. In support of this hypothesis, we found that the addition of either of the acetyl donors acetyl phosphate and acetyl-coenzyme A inhibits translation but not transcription using an E. coli cell-free system. Further investigations using assays revealed that acetylation does not appear to alter the rate of translation elongation but, rather, increases the proportions of dissociated 30S and 50S ribosomes, based on polysome profiles of mutants or growth conditions known to promote lysine acetylation. Furthermore, ribosomal proteins are more acetylated in the disassociated 30S and 50S ribosomal subunits than in the fully assembled 70S complex. The effect of acetylation is also growth rate dependent, with disassociation of the subunits being most pronounced during late-exponential and early-stationary-phase growth-the same growth phase where protein acetylation is greatest. Collectively, our data demonstrate that lysine acetylation inhibits translation, most likely by interfering with subunit association. These results have also uncovered a new mechanism for coupling translation to the metabolic state of the cell. Numerous cellular processes are regulated in response to the metabolic state of the cell. One such regulatory mechanism involves lysine acetylation, a covalent modification involving the transfer of an acetyl group from central metabolite acetyl-coenzyme A or acetyl phosphate to a lysine residue in a protein. This posttranslational modification is known to regulate some central metabolic enzymes and transcription factors in bacteria, though a comprehensive understanding of its effect on cellular physiology is still lacking. In the present study, lysine acetylation was also found to inhibit translation in Escherichia coli by impeding ribosome association, most likely by disrupting salt bridges along the binding interface of the 30S and 50S ribosomal subunits. These results further our understanding of lysine acetylation by uncovering protein synthesis as a new target of regulation and aid in the design of bacteria for biotechnology applications where the growth conditions are known to promote lysine acetylation.
ε-赖氨酸乙酰化是一种在多种细菌中普遍存在的翻译后修饰。除了少数中心代谢酶和转录因子外，人们对这种翻译后修饰如何调节蛋白质活性知之甚少。在这项工作中，我们研究了赖氨酸乙酰化如何影响大肠杆菌中的翻译。在多种细菌中，核糖体蛋白在保守的赖氨酸残基上高度乙酰化，这表明这种修饰可能调节翻译。为了支持这一假设，我们发现添加乙酰磷酸或乙酰辅酶 A 这两种乙酰供体之一都会抑制大肠杆菌无细胞系统中的翻译，但不抑制转录。进一步的研究使用测定法表明，乙酰化似乎不会改变翻译延伸的速度，而是增加了解离的 30S 和 50S 核糖体的比例，这是基于突变体或已知促进赖氨酸乙酰化的生长条件的多核糖体图谱。此外，核糖体蛋白在解离的 30S 和 50S 核糖体亚基中比在完全组装的 70S 复合物中更容易乙酰化。乙酰化的影响也与生长速率有关，亚基的解离在对数晚期和早期稳定期最为明显——这是蛋白质乙酰化程度最高的生长阶段。总的来说，我们的数据表明赖氨酸乙酰化抑制翻译，这很可能是通过干扰亚基的结合来实现的。这些结果还揭示了一种将翻译与细胞代谢状态相耦合的新机制。许多细胞过程都受到细胞代谢状态的调节。一种这样的调节机制涉及赖氨酸乙酰化，这是一种涉及将乙酰基从中心代谢物乙酰辅酶 A 或乙酰磷酸转移到蛋白质中赖氨酸残基上的共价修饰。这种翻译后修饰已知可以调节细菌中的一些中心代谢酶和转录因子，尽管人们对其对细胞生理学的影响仍缺乏全面的了解。在本研究中，还发现赖氨酸乙酰化通过阻碍核糖体的结合来抑制大肠杆菌中的翻译，这很可能是通过破坏 30S 和 50S 核糖体亚基结合界面上的盐桥来实现的。这些结果通过揭示蛋白质合成作为新的调控靶点，进一步加深了我们对赖氨酸乙酰化的理解，并有助于设计生物技术应用中的细菌，这些细菌的生长条件已知可以促进赖氨酸乙酰化。
