Kawamoto Akihiro, Morimoto Yusuke V, Miyata Tomoko, Minamino Tohru, Hughes Kelly T, Kato Takayuki, Namba Keiichi
1] Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan [2] Riken Quantitative Biology Center, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
Sci Rep. 2013 Nov 28;3:3369. doi: 10.1038/srep03369.
Bacterial pathogens use an injectisome to deliver virulence proteins into eukaryotic host cells. The bacterial flagellum and injectisome export their component proteins for self-assembly. These two systems show high structural similarities and are classified as the type III secretion system, but it remains elusive how similar they are in situ because the structures of these complexes isolated from cells and visualized by electron cryomicroscopy have shown only the export channel and housing for the export apparatus. Here we report in situ structures of Salmonella injectisome and flagellum by electron cryotomography. The injectisome lacks the flagellar basal body C-ring, but a wing-like disc and a globular density corresponding to the export gate platform and ATPase hexamer ring, respectively, are stably attached through thin connectors, revealing yet unidentified common architectures of the two systems. The ATPase ring is far from the disc, suggesting that both apparatuses are observed in an export-off state.
细菌病原体利用注射体将毒力蛋白输送到真核宿主细胞中。细菌鞭毛和注射体通过输出其组成蛋白进行自我组装。这两个系统在结构上有高度相似性，被归类为III型分泌系统，但它们在原位的相似程度仍不清楚，因为通过电子冷冻显微镜从细胞中分离并可视化的这些复合物的结构仅显示了输出通道和输出装置的外壳。在此，我们通过电子冷冻断层扫描报告了沙门氏菌注射体和鞭毛的原位结构。注射体缺乏鞭毛基体C环，但分别对应于输出门平台和ATP酶六聚体环的一个翼状盘和一个球状致密物通过细连接体稳定连接，揭示了这两个系统尚未明确的共同结构。ATP酶环远离盘状物，表明这两种装置均处于输出关闭状态。
