Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
J Bacteriol. 2013 May;195(10):2126-35. doi: 10.1128/JB.00032-13. Epub 2013 Mar 1.
Pseudomonas aeruginosa type IV pili (T4P) are virulence factors that promote infection of cystic fibrosis and immunosuppressed patients. As the absence of T4P impairs colonization, they are attractive targets for the development of novel therapeutics. Genes in the pilMNOPQ operon are important for both T4P assembly and a form of bacterial movement, called twitching motility, that is required for pathogenicity. The type II membrane proteins, PilN and PilO, dimerize via their periplasmic domains and anchor this complex in the inner membrane. Our earlier work showed that PilNO binds PilP, a periplasmic lipoprotein (S. Tammam, L. M. Sampaleanu, J. Koo, P. Sundaram, M. Ayers, P. A. Chong, J. D. Forman-Kay, L. L. Burrows, and P. L. Howell, Mol. Microbiol. 82:1496-1514, 2011). Here, we show that PilP interacts with the N0 segment of the outer membrane secretin PilQ via its C-terminal domain, and that the N-terminal cytoplasmic tail of PilN binds to the actin-like protein PilM, thereby connecting all cellular compartments via the PilMNOPQ protein interaction network. We show that PilA, the major pilin subunit, interacts with PilNOPQ. The results allow us to propose a model whereby PilA makes extensive contacts with the transenvelope complex, possibly to increase local concentrations of PilA monomers for polymerization. The PilNOP complex could provide a stable anchor in the inner membrane, while the PilMNOPQ transenvelope complex facilitates transit of the pilus through the periplasm and clamps the pilus in the cell envelope. The PilMN interaction is proposed to be responsible for communicating signals from the cytoplasmic to periplasmic components of this complex macromolecular machine.
铜绿假单胞菌 IV 型菌毛（T4P）是促进囊性纤维化和免疫抑制患者感染的毒力因子。由于 T4P 的缺失会损害定植，因此它们是开发新型治疗药物的有吸引力的靶标。 pilMNOPQ 操纵子中的基因对于 T4P 组装和一种称为 twitching motility 的细菌运动形式都很重要，这种运动形式对于致病性是必需的。II 型膜蛋白 PilN 和 PilO 通过其周质域二聚化，并将该复合物锚定在内膜中。我们之前的工作表明，PilNO 结合了周质脂蛋白 PilP（S. Tammam、L. M. Sampaleanu、J. Koo、P. Sundaram、M. Ayers、P. A. Chong、J. D. Forman-Kay、L. L. Burrows 和 P. L. Howell，Mol. Microbiol. 82:1496-1514, 2011）。在这里，我们表明 PilP 通过其 C 端结构域与外膜分泌孔蛋白 PilQ 的 N0 段相互作用，并且 PilN 的 N 端细胞质尾巴与肌动蛋白样蛋白 PilM 结合，从而通过 PilMNOPQ 蛋白相互作用网络连接所有细胞区室。我们表明主要的菌毛亚基 PilA 与 PilNOPQ 相互作用。这些结果使我们能够提出一个模型，即 PilA 与跨膜复合物广泛接触，可能会增加 PilA 单体聚合的局部浓度。PilNOP 复合物可以在内膜中提供稳定的锚点，而 PilMNOPQ 跨膜复合物则促进菌毛穿过周质并将菌毛夹在细胞包膜中。拟议的 PilMN 相互作用负责将信号从细胞质传递到该复杂大分子机器的周质成分。
