Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée CNRS - UMR 7255 Aix-Marseille University, Marseille, France.
EMBO Rep. 2014 Mar;15(3):315-21. doi: 10.1002/embr.201337936. Epub 2014 Jan 31.
The Type VI secretion system (T6SS) is a widespread macromolecular structure that delivers protein effectors to both eukaryotic and prokaryotic recipient cells. The current model describes the T6SS as an inverted phage tail composed of a sheath-like structure wrapped around a tube assembled by stacked Hcp hexamers. Although recent progress has been made to understand T6SS sheath assembly and dynamics, there is no evidence that Hcp forms tubes in vivo. Here we show that Hcp interacts with TssB, a component of the T6SS sheath. Using a cysteine substitution approach, we demonstrate that Hcp hexamers assemble tubes in an ordered manner with a head-to-tail stacking that are used as a scaffold for polymerization of the TssB/C sheath-like structure. Finally, we show that VgrG but not TssB/C controls the proper assembly of the Hcp tubular structure. These results highlight the conservation in the assembly mechanisms between the T6SS and the bacteriophage tail tube/sheath.
VI 型分泌系统（T6SS）是一种广泛存在的大分子结构，可将蛋白效应器输送到真核和原核受体细胞。目前的模型将 T6SS 描述为一个倒置的噬菌体尾部，由一个鞘状结构包裹在由堆叠的 Hcp 六聚体组装而成的管周围。尽管最近在理解 T6SS 鞘的组装和动力学方面取得了进展，但没有证据表明 Hcp 在体内形成管。在这里，我们表明 Hcp 与 T6SS 鞘的组成部分 TssB 相互作用。通过半胱氨酸取代方法，我们证明 Hcp 六聚体以有序的方式组装成管状结构，头对头堆叠，作为 TssB/C 鞘状结构聚合的支架。最后，我们表明 VgrG 而不是 TssB/C 控制 Hcp 管状结构的正确组装。这些结果强调了 T6SS 和噬菌体尾部管/鞘之间在组装机制上的保守性。
