Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, Pasadena, CA 91125, USA.
Cell Rep. 2018 Apr 17;23(3):673-681. doi: 10.1016/j.celrep.2018.03.085.
The type IV secretion system (T4SS) is a versatile nanomachine that translocates diverse effector molecules between microbes and into eukaryotic cells. Here, using electron cryotomography, we reveal the molecular architecture of the Helicobacter pylori cag T4SS. Although most components are unique to H. pylori, the cag T4SS exhibits remarkable architectural similarity to other T4SSs. Our images revealed that, when H. pylori encounters host cells, the bacterium elaborates membranous tubes perforated by lateral ports. Sub-tomogram averaging of the cag T4SS machinery revealed periplasmic densities associated with the outer membrane, a central stalk, and peripheral wing-like densities. Additionally, we resolved pilus-like rod structures extending from the cag T4SS into the inner membrane, as well as densities within the cytoplasmic apparatus corresponding to a short central barrel surrounded by four longer barrels. Collectively, these studies reveal the structure of a dynamic molecular machine that evolved to function in the human gastric niche.
IV 型分泌系统（T4SS）是一种多功能纳米机器，可在微生物之间以及将各种效应分子易位到真核细胞中。在这里，我们使用电子晶体学来揭示幽门螺杆菌 cag T4SS 的分子结构。尽管大多数组件是幽门螺杆菌所独有的，但 cag T4SS 表现出与其他 T4SS 惊人的结构相似性。我们的图像显示，当幽门螺杆菌遇到宿主细胞时，细菌会精心设计穿孔的膜管。对 cag T4SS 机械装置的子断层平均法揭示了与外膜、中央柄和外围翼状密度相关的周质密度。此外，我们还解析了从 cag T4SS 延伸到内膜的类似于菌毛的杆状结构，以及细胞质装置内与短中心桶周围的四个较长桶相对应的密度。总的来说，这些研究揭示了一种动态分子机器的结构，这种机器进化为在人类胃腔中发挥作用。
