Contractile injection systems (CISs) [type VI secretion system (T6SS), phage tails, and tailocins] use a contractile sheath-rigid tube machinery to breach cell walls and lipid membranes. The structures of the pre- and postcontraction states of several CISs are known, but the mechanism of contraction remains poorly understood. Combining structural information of the end states of the 12-megadalton R-type pyocin sheath-tube complex with thermodynamic and force spectroscopy analyses and an original modeling procedure, we describe the mechanism of pyocin contraction. We show that this nanomachine has an activation energy of 160 kilocalories/mole (kcal/mol), and it releases 2160 kcal/mol of heat and develops a force greater than 500 piconewtons. Our combined approach provides a quantitative and experimental description of the membrane penetration process by a CIS.

收缩注射系统 (CIS) [VI 型分泌系统 (T6SS)、噬菌体尾巴和 tailocins] 使用收缩鞘-刚性管机械来破坏细胞壁和脂质膜。几个 CIS 收缩前和收缩后状态的结构是已知的，但收缩机制仍然知之甚少。将 12 兆道尔顿 R 型脓菌素鞘管复合物的最终状态的结构信息与热力学和力谱分析以及原始建模程序相结合，我们描述了脓菌素收缩的机制。我们表明，这种纳米机器具有 160 千卡/摩尔 (kcal/mol) 的活化能，它释放 2160 kcal/mol 的热量并产生大于 500 皮牛顿的力。