Department of Microbiology and Immunobiology, Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts 02115, USA.
Nature. 2012 Feb 26;483(7388):182-6. doi: 10.1038/nature10846.
Type VI secretion systems are bacterial virulence-associated nanomachines composed of proteins that are evolutionarily related to components of bacteriophage tails. Here we show that protein secretion by the type VI secretion system of Vibrio cholerae requires the action of a dynamic intracellular tubular structure that is structurally and functionally homologous to contractile phage tail sheath. Time-lapse fluorescence light microscopy reveals that sheaths of the type VI secretion system cycle between assembly, quick contraction, disassembly and re-assembly. Whole-cell electron cryotomography further shows that the sheaths appear as long tubular structures in either extended or contracted conformations that are connected to the inner membrane by a distinct basal structure. These data support a model in which the contraction of the type VI secretion system sheath provides the energy needed to translocate proteins out of effector cells and into adjacent target cells.
VI 型分泌系统是一种与细菌毒力相关的纳米机器，由与噬菌体尾部组件在进化上相关的蛋白质组成。在这里，我们表明，霍乱弧菌 VI 型分泌系统的蛋白质分泌需要一种动态的细胞内管状结构的作用，该结构在结构和功能上与收缩性噬菌体尾鞘同源。延时荧光显微镜显示，VI 型分泌系统的鞘在组装、快速收缩、解体和再组装之间循环。全细胞电子晶体断层扫描进一步表明，鞘呈现出长管状结构，无论是伸展还是收缩构象，都通过一个明显的基底结构与内膜相连。这些数据支持了这样一种模型，即 VI 型分泌系统鞘的收缩提供了将蛋白质从效应细胞转运到相邻靶细胞所需的能量。
