Orthosomycin antibiotics inhibit protein synthesis by binding to the large ribosomal subunit in the tRNA accommodation corridor, which is traversed by incoming aminoacyl-tRNAs. Structural and biochemical studies suggested that orthosomycins block accommodation of any aminoacyl-tRNAs in the ribosomal A-site. However, the mode of action of orthosomycins in vivo remained unknown. Here, by carrying out genome-wide analysis of antibiotic action in bacterial cells, we discovered that orthosomycins primarily inhibit the ribosomes engaged in translation of specific amino acid sequences. Our results reveal that the predominant sites of orthosomycin-induced translation arrest are defined by the nature of the incoming aminoacyl-tRNA and likely by the identity of the two C-terminal amino acid residues of the nascent protein. We show that nature exploits this antibiotic-sensing mechanism for directing programmed ribosome stalling within the regulatory open reading frame, which may control expression of an orthosomycin-resistance gene in a variety of bacterial species.

正霉素抗生素通过结合 tRNA 调节通道中的大核糖体亚基来抑制蛋白质合成，进入的氨酰-tRNA 会穿过该通道。结构和生化研究表明，orthosomycins 可阻断核糖体 A 位点中任何氨酰 tRNA 的调节。然而，orthosomycins 在体内的作用方式仍然未知。在这里，通过对细菌细胞中的抗生素作用进行全基因组分析，我们发现 orthosomycins 主要抑制参与特定氨基酸序列翻译的核糖体。我们的结果表明，orthosomycin 诱导的翻译停滞的主要位点由传入的氨酰-tRNA 的性质决定，并且可能由新生蛋白的两个 C 末端氨基酸残基的特性决定。