Department of Cell and Molecular Biology, Uppsala University, Uppsala, SE-75124, Sweden.
Nat Commun. 2023 Feb 17;14(1):918. doi: 10.1038/s41467-023-36528-7.
Thermorubin (THB) is a long-known broad-spectrum ribosome-targeting antibiotic, but the molecular mechanism of its action was unclear. Here, our precise fast-kinetics assays in a reconstituted Escherichia coli translation system and 1.96 Å resolution cryo-EM structure of THB-bound 70S ribosome with mRNA and initiator tRNA, independently suggest that THB binding at the intersubunit bridge B2a near decoding center of the ribosome interferes with the binding of A-site substrates aminoacyl-tRNAs and class-I release factors, thereby inhibiting elongation and termination steps of bacterial translation. Furthermore, THB acts as an anti-dissociation agent that tethers the ribosomal subunits and blocks ribosome recycling, subsequently reducing the pool of active ribosomes. Our results show that THB does not inhibit translation initiation as proposed earlier and provide a complete mechanism of how THB perturbs bacterial protein synthesis. This in-depth characterization will hopefully spur efforts toward the design of THB analogs with improved solubility and effectivity against multidrug-resistant bacteria.
热稳定红菌素（Thermorubin，THB）是一种广谱核糖体靶向抗生素，但它的作用机制尚不清楚。在这里，我们在体外重建的大肠杆菌翻译系统中进行了精确的快速动力学检测，并解析了 THB 结合到含有 mRNA 和起始 tRNA 的 70S 核糖体的冷冻电镜结构（分辨率为 1.96Å），这两项独立的研究结果均表明，THB 与核糖体亚基间 B2a 桥的结合，干扰了氨酰基-tRNA 进入 A 位以及Ⅰ类释放因子的释放，从而抑制了细菌翻译的延伸和终止步骤。此外，THB 作为一种抗解离剂，可连接核糖体亚基并阻止核糖体的再循环，从而减少活性核糖体的数量。我们的研究结果表明，THB 并不像之前提出的那样抑制翻译起始，而是提供了一个完整的作用机制，说明了 THB 如何干扰细菌的蛋白质合成。对其进行深入的研究，有望推动设计出具有更好溶解性和针对多重耐药菌的有效性的 THB 类似物。
