小组报道了无DNA、单链DNA （ssDNA）结合和双链DNA （dsDNA）结合形式的ComEC的低温电镜结构，以及生化分析。这些结构揭示了ComEC在其细胞外区域切割一条dsDNA链，并将剩余的链引导到膜区域内形成的带正电的孔中。这些发现为长期假设的ComEC在自然转化过程中DNA加工和跨内膜易位中的作用提供了结构基础。
研究人员表示，自然转化是细菌水平基因转移的主要途径之一，能够获得细胞外DNA并将其整合到宿主基因组中。ComEC是在这一过程中负责DNA易位的膜蛋白，但其精确的功能和结构仍然是未知的。
附：英文原文
Title: Structural basis for DNA processing and membrane translocation by ComEC in natural transformation
Author: Hisato Hirano, Naoko Tsuji, Shinobu Chiba, Osamu Nureki
Issue&Volume: 2026-04-16
Abstract: Natural transformation is one of the major pathways of horizontal gene transfer in bacteria, enabling the acquisition of extracellular DNA and its integration into the host genome. ComEC is a membrane protein responsible for DNA translocation in this process, yet its precise function and structure have remained elusive. Here, we report cryo–electron microscopy structures of ComEC in DNA-free, single-stranded DNA (ssDNA)–bound, and double-stranded DNA (dsDNA)–bound forms, together with biochemical analyses. These structures reveal that ComEC cleaves one strand of dsDNA at its extracellular domain and guides the remaining strand into a positively charged pore formed within the membrane domain. These findings provide a structural basis for the long-hypothesized roles of ComEC in both DNA processing and translocation across the inner membrane during natural transformation.
DOI: aea3485
Source: https://www.science.org/doi/10.1126/science.aea3485