Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, 277-8562, Japan.
Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Nat Commun. 2020 Oct 28;11(1):5438. doi: 10.1038/s41467-020-19281-z.
Toxin-antitoxin systems in bacteria contribute to stress adaptation, dormancy, and persistence. AtaT, a type-II toxin in enterohemorrhagic E. coli, reportedly acetylates the α-amino group of the aminoacyl-moiety of initiator Met-tRNAf, thus inhibiting translation initiation. Here, we show that AtaT has a broader specificity for aminoacyl-tRNAs than initially claimed. AtaT efficiently acetylates Gly-tRNA, Trp-tRNA, Tyr-tRNA and Phe-tRNA isoacceptors, in addition to Met-tRNAf, and inhibits global translation. AtaT interacts with the acceptor stem of tRNAf, and the consecutive G-C pairs in the bottom-half of the acceptor stem are required for acetylation. Consistently, tRNA, tRNA, tRNA and tRNA also possess consecutive G-C base-pairs in the bottom halves of their acceptor stems. Furthermore, misaminoacylated valyl-tRNAf and isoleucyl-tRNAf are not acetylated by AtaT. Therefore, the substrate selection by AtaT is governed by the specific acceptor stem sequence and the properties of the aminoacyl-moiety of aminoacyl-tRNAs.
细菌中的毒素-抗毒素系统有助于应激适应、休眠和持续存在。肠出血性大肠杆菌中的 AtaT 是一种 II 型毒素，据报道它乙酰化起始 Met-tRNAf 的氨酰基部分的α-氨基，从而抑制翻译起始。在这里，我们表明 AtaT 对氨酰-tRNA 的特异性比最初声称的更广泛。AtaT 可有效乙酰化 Gly-tRNA、Trp-tRNA、Tyr-tRNA 和 Phe-tRNA 同工受体，除了 Met-tRNAf，并抑制全局翻译。AtaT 与 tRNAf 的接受茎相互作用，并且接受茎下半部分的连续 G-C 对对于乙酰化是必需的。一致地，tRNA、tRNA、tRNA 和 tRNA 也在它们的接受茎的下半部分具有连续的 G-C 碱基对。此外，错误氨酰化的缬氨酰-tRNAf 和异亮氨酰-tRNAf 不受 AtaT 乙酰化。因此，AtaT 的底物选择受特定的接受茎序列和氨酰-tRNA 的氨酰基部分的性质控制。
