Center for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Center for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Structure. 2024 Oct 3;32(10):1725-1736.e4. doi: 10.1016/j.str.2024.06.019. Epub 2024 Jul 19.
Cag type IV secretion system (CagT4SS) translocates oncoprotein cytotoxin-associated gene A (CagA) into host cells and plays a key role in the pathogenesis of Helicobacter pylori. The structure of the outer membrane core complex (OMCC) in CagT4SS consists of CagX, CagY, CagM, CagT, and Cag3 in a stoichiometric ratio of 1:1:2:2:5 with 14-fold symmetry. However, the assembly pathway of OMCC remains elusive. Here, we report the crystal structures of CagT and Cag3-CagT complex, and the structural dynamics of Cag3 and CagT using hydrogen deuterium exchange-mass spectrometry (HDX-MS). The interwoven interaction of Cag3 and CagT involves conformational changes of CagT and β strand swapping. In conjunction with biochemical and biophysical assays, we further demonstrate the different oligomerization states of Cag3 and Cag3-CagT complex. Additionally, the association with CagM requires the pre-formation of Cag3-CagT complex. These results demonstrate the generation of different intermediate sub-assemblies and their structural flexibility, potentially representing different building blocks for OMCC assembly.
Cag 型 IV 型分泌系统 (CagT4SS) 将癌蛋白细胞毒素相关基因 A (CagA) 易位到宿主细胞中，在幽门螺杆菌的发病机制中发挥关键作用。CagT4SS 的外膜核心复合物 (OMCC) 的结构由 CagX、CagY、CagM、CagT 和 Cag3 以 1:1:2:2:5 的比例等摩尔比组成，具有 14 重对称。然而，OMCC 的组装途径仍然难以捉摸。在这里，我们报告了 CagT 和 Cag3-CagT 复合物的晶体结构，以及使用氢氘交换质谱 (HDX-MS) 的 Cag3 和 CagT 的结构动力学。Cag3 和 CagT 的交织相互作用涉及 CagT 的构象变化和 β 链交换。结合生化和生物物理测定，我们进一步证明了 Cag3 和 Cag3-CagT 复合物的不同寡聚状态。此外，与 CagM 的结合需要 Cag3-CagT 复合物的预先形成。这些结果表明产生了不同的中间亚组装体及其结构灵活性，可能代表 OMCC 组装的不同构建块。
