MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou, Guangdong 510006, People's Republic of China.
State Key Laboratory of Oncology in South China, Sun Yat-Sen University Cancer Center, 651 E. Dongfeng Road, Guangzhou, Guangdong 510060, People's Republic of China.
ACS Infect Dis. 2020 Jul 10;6(7):1783-1795. doi: 10.1021/acsinfecdis.0c00048. Epub 2020 Jun 16.
Toxin-antitoxin (TA) systems, which regulate many important cellular processes, are abundantly present in prokaryotic organisms. MazEF is a common type of TA system implicated in the formation of "persisters cells" of the pathogen , which contains 10 such systems. However, the exact function and inhibition mode of each MazF protein are not quite understood. Here, we report four high-resolution crystal structures of MazF-mt1 in various forms, including one in complex with MazE-mt1. The toxin displayed two unique interlocked loops that allow the formation of a tight dimer. These loops would open upon interacting with the MazE-mt1 antitoxin mediated by the last two helices of MazE-mt1. With our structure-based design, a mutant that could bind to the antitoxin with an enhanced affinity was produced. Combined crystallographic and biochemical studies further revealed that the binding affinity of MazE-mt1 to MazF-mt1 was mainly attributed to its α3 helical region, while the terminal helix η1 contributes very little or even negatively to the association of the pair, in stark contrast to the MazEF-mt9 system. This study provides structural insight into the binding mode and the inhibition mechanism of the MazE/F-mt1 TA pair, which may reflect the functional differences between different TA systems.
毒素-抗毒素 (TA) 系统调节着许多重要的细胞过程，在原核生物中大量存在。MazEF 是一种常见的 TA 系统，与病原体形成“持久细胞”有关，其中包含 10 个这样的系统。然而，每个 MazF 蛋白的确切功能和抑制模式尚不完全清楚。在这里，我们报告了四种不同形式的 MazF-mt1 的高分辨率晶体结构，包括一种与 MazE-mt1 复合物的结构。毒素显示出两个独特的互锁环，允许形成紧密的二聚体。这些环在 MazE-mt1 最后两个螺旋介导下与 MazE-mt1 抗毒素相互作用时会打开。基于我们的结构设计，产生了一种能够与抗毒素结合的突变体，其亲和力增强。结合晶体学和生化研究进一步表明，MazE-mt1 与 MazF-mt1 的结合亲和力主要归因于其 α3 螺旋区域，而末端螺旋 η1 对该对的结合几乎没有贡献，甚至产生负面影响，与 MazEF-mt9 系统形成鲜明对比。这项研究提供了对 MazE/F-mt1 TA 对结合模式和抑制机制的结构见解，这可能反映了不同 TA 系统之间的功能差异。
