School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Nucleic Acids Res. 2022 Jun 10;50(10):5948-5960. doi: 10.1093/nar/gkac442.
The cell-wall recycling process is important for bacterial survival in nutrient-limited conditions and, in certain cases, is directly involved in antibiotic resistance. In the sophisticated cell-wall recycling process in Escherichia coli, the transcriptional repressor MurR controls the expression of murP and murQ, which are involved in transporting and metabolizing N-acetylmuramic acid (MurNAc), generating N-acetylmuramic acid-6-phosphate (MurNAc-6-P) and N-acetylglucosamine-6-phosphate (GlcNAc-6-P). Here, we report that both MurNAc-6-P and GlcNAc-6-P can bind to MurR and weaken the DNA binding ability of MurR. Structural characterizations of MurR in complex with MurNAc-6-P or GlcNAc-6-P as well as in the apo form revealed the detailed ligand recognition chemistries. Further studies showed that only MurNAc-6-P, but not GlcNAc-6-P, is capable of derepressing the expression of murQP controlled by MurR in cells and clarified the substrate specificity through the identification of key residues responsible for ligand binding in the complex structures. In summary, this study deciphered the molecular mechanism of the cell wall recycling process regulated by MurR in E. coli.
细胞壁回收过程对于细菌在营养有限的条件下的生存至关重要，在某些情况下，它直接参与抗生素耐药性的产生。在大肠杆菌复杂的细胞壁回收过程中，转录抑制剂 MurR 控制着 murP 和 murQ 的表达，murP 和 murQ 参与了 N-乙酰胞壁酸（MurNAc）的转运和代谢，生成 N-乙酰胞壁酸-6-磷酸（MurNAc-6-P）和 N-乙酰葡萄糖胺-6-磷酸（GlcNAc-6-P）。在这里，我们报告 MurNAc-6-P 和 GlcNAc-6-P 都可以与 MurR 结合，并削弱 MurR 的 DNA 结合能力。MurR 与 MurNAc-6-P 或 GlcNAc-6-P 复合物以及无配体形式的结构特征揭示了详细的配体识别化学性质。进一步的研究表明，只有 MurNAc-6-P，而不是 GlcNAc-6-P，能够在细胞中解除 MurR 对 murQP 表达的抑制，并通过鉴定复合物结构中负责配体结合的关键残基阐明了底物特异性。总之，本研究揭示了 MurR 调节大肠杆菌细胞壁回收过程的分子机制。
