Bacteria need to deliver large molecules out of the cytosol to the extracellular space or even across membranes of neighboring cells to influence their environment, prevent predation, defeat competitors, or communicate. A variety of protein-secretion systems have evolved to make this process highly regulated and efficient. The type VI secretion system (T6SS) is one of the largest dynamic assemblies in gram-negative bacteria and allows for delivery of toxins into both bacterial and eukaryotic cells. The recent progress in structural biology and live-cell imaging shows the T6SS as a long contractile sheath assembled around a rigid tube with associated toxins anchored to a cell envelope by a baseplate and membrane complex. Rapid sheath contraction releases a large amount of energy used to push the tube and toxins through the membranes of neighboring target cells. Because reach of the T6SS is limited, some bacteria dynamically regulate its subcellular localization to precisely aim at their targets and thus increase efficiency of toxin translocation.

中文翻译：

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第六类细菌分泌系统的组装和亚细胞定位。

细菌需要将大分子从胞质溶胶中传递到细胞外空间，甚至跨邻近细胞的膜传递，以影响其环境，防止被捕食，击败竞争对手或进行交流。已经开发出多种蛋白质分泌系统，以使该过程受到高度调节和有效。VI型分泌系统（T6SS）是革兰氏阴性细菌中最大的动态组件之一，可将毒素传递到细菌和真核细胞中。结构生物学和活细胞成像的最新进展表明，T6SS是围绕刚性管组装的长而收缩的鞘，其相关毒素通过底板和膜复合物锚定在细胞膜上。快速的鞘收缩释放大量能量，该能量用于推动管子和毒素穿过邻近靶细胞的膜。由于T6SS的作用范围有限，因此某些细菌会动态调节其亚细胞定位，以精确地瞄准它们的靶标，从而提高毒素转运的效率。