Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
J Mol Biol. 2019 May 3;431(10):1956-1965. doi: 10.1016/j.jmb.2019.03.029. Epub 2019 Apr 5.
Helicobacter pylori colonizes the human stomach and contributes to the development of gastric cancer and peptic ulcer disease. H. pylori secretes a pore-forming toxin called vacuolating cytotoxin A (VacA), which contains two domains (p33 and p55) and assembles into oligomeric structures. Using single-particle cryo-electron microscopy, we have determined low-resolution structures of a VacA dodecamer and heptamer, as well as a 3.8-Å structure of the VacA hexamer. These analyses show that VacA p88 consists predominantly of a right-handed beta-helix that extends from the p55 domain into the p33 domain. We map the regions of p33 and p55 involved in hexamer assembly, model how interactions between protomers support heptamer formation, and identify surfaces of VacA that likely contact membrane. This work provides structural insights into the process of VacA oligomerization and identifies regions of VacA protomers that are predicted to contact the host cell surface during channel formation.
幽门螺杆菌定植于人类胃部，并导致胃癌和消化性溃疡病的发生。幽门螺杆菌分泌一种称为空泡细胞毒素 A（VacA）的形成孔的毒素，该毒素包含两个结构域（p33 和 p55）并组装成寡聚体结构。使用单颗粒冷冻电子显微镜，我们已经确定了 VacA 十二聚体和七聚体的低分辨率结构，以及 VacA 六聚体的 3.8 Å 结构。这些分析表明，VacA p88 主要由右手β-螺旋组成，该螺旋从 p55 结构域延伸到 p33 结构域。我们绘制了参与六聚体组装的 p33 和 p55 区域的图谱，模拟了单体之间的相互作用如何支持七聚体的形成，并确定了 VacA 与膜相互作用的表面。这项工作提供了 VacA 寡聚化过程的结构见解，并确定了 VacA 单体在通道形成过程中预测与宿主细胞表面相互作用的区域。
