Department of Biochemistry, University of Oxford, Oxford, UK.
Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
Mol Microbiol. 2021 Aug;116(2):416-426. doi: 10.1111/mmi.14720. Epub 2021 Jun 4.
In the process of natural transformation bacteria import extracellular DNA molecules for integration into their genome. One strand of the incoming DNA molecule is degraded, whereas the remaining strand is transported across the cytoplasmic membrane. The DNA transport channel is provided by the protein ComEC. Many ComEC proteins have an extracellular C-terminal domain (CTD) with homology to the metallo-β-lactamase fold. Here we show that this CTD binds Mn ions and exhibits Mn -dependent phosphodiesterase and nuclease activities. Inactivation of the enzymatic activity of the CTD severely inhibits natural transformation in Bacillus subtilis. These data suggest that the ComEC CTD is a nuclease responsible for degrading the nontransforming DNA strand during natural transformation and that this process is important for efficient DNA import.
在自然转化过程中，细菌会摄取细胞外的 DNA 分子并将其整合到基因组中。进入的 DNA 分子的一条链被降解，而另一条链则穿过细胞质膜进行运输。DNA 运输通道由 ComEC 蛋白提供。许多 ComEC 蛋白具有与金属β-内酰胺酶折叠同源的细胞外 C 端结构域（CTD）。在这里，我们表明该 CTD 结合 Mn 离子，并表现出 Mn 依赖性的磷酸二酯酶和核酸酶活性。CTD 的酶活性失活严重抑制枯草芽孢杆菌中的自然转化。这些数据表明，ComEC CTD 是一种核酸酶，负责在自然转化过程中降解非转化的 DNA 链，并且该过程对于有效导入 DNA 是重要的。
