Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France.
Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK.
Nat Commun. 2023 Aug 17;14(1):4644. doi: 10.1038/s41467-023-40264-3.
Mycobacterium tuberculosis, the bacterium responsible for human tuberculosis, has a genome encoding a remarkably high number of toxin-antitoxin systems of largely unknown function. We have recently shown that the M. tuberculosis genome encodes four of a widespread, MenAT family of nucleotidyltransferase toxin-antitoxin systems. In this study we characterize MenAT1, using tRNA sequencing to demonstrate MenT1 tRNA modification activity. MenT1 activity is blocked by MenA1, a short protein antitoxin unrelated to the MenA3 kinase. X-ray crystallographic analysis shows blockage of the conserved MenT fold by asymmetric binding of MenA1 across two MenT1 protomers, forming a heterotrimeric toxin-antitoxin complex. Finally, we also demonstrate tRNA modification by toxin MenT4, indicating conserved activity across the MenT family. Our study highlights variation in tRNA target preferences by MenT toxins, selective use of nucleotide substrates, and diverse modes of MenA antitoxin activity.
结核分枝杆菌是导致人类结核病的细菌，其基因组编码了大量功能未知的毒素-抗毒素系统。我们最近表明，结核分枝杆菌基因组编码了四个广泛存在的 MenAT 家族核苷酸转移酶毒素-抗毒素系统。在这项研究中，我们使用 tRNA 测序来证明 MenT1 的 tRNA 修饰活性，对 MenAT1 进行了表征。MenT1 的活性被与 MenA3 激酶无关的短蛋白抗毒素 MenA1 阻断。X 射线晶体学分析表明，MenA1 不对称地结合两个 MenT1 三聚体，阻断了保守的 MenT 折叠，形成了一个异源三聚体毒素-抗毒素复合物。最后，我们还证明了毒素 MenT4 对 tRNA 的修饰，表明了 MenT 家族在活性上的保守性。我们的研究强调了 MenT 毒素对 tRNA 靶标偏好的变化、核苷酸底物的选择性使用以及不同的 MenA 抗毒素活性模式。
