Saulino E T, Bullitt E, Hultgren S J
Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, St. Louis, MO 63110-1010, USA.
Proc Natl Acad Sci U S A. 2000 Aug 1;97(16):9240-5. doi: 10.1073/pnas.160070497.
Type 1 pilus biogenesis was used as a paradigm to investigate ordered macromolecular assembly at the outer cell membrane. The ability of Gram-negative bacteria to secrete proteins across their outer membrane and to assemble adhesive macromolecular structures on their surface is a defining event in pathogenesis. We elucidated genetic, biochemical, and biophysical requirements for assembly of functional type 1 pili. We discovered that the minor pilus protein FimG plays a critical role in nucleating the formation of the adhesive tip fibrillum. Genetic methods were used to trap pilus subunits during their translocation through the outer membrane usher protein, providing data on the structural interactions that occur between subunit components during type 1 pilus formation. Electron microscopic and biochemical analyses of these stepwise assembly intermediates demonstrated that translocation of pilus subunits occurs linearly through the usher's central channel, with formation of the pilus helix occurring extracellularly. Specialized pilin subunits play unique roles both in this multimerization and in the final ultrastructure of the adhesive pilus.
1型菌毛生物合成被用作研究外细胞膜上有序大分子组装的范例。革兰氏阴性菌跨外膜分泌蛋白质并在其表面组装粘附性大分子结构的能力是发病机制中的一个决定性事件。我们阐明了功能性1型菌毛组装的遗传、生化和生物物理要求。我们发现次要菌毛蛋白FimG在粘附性尖端纤维的成核形成中起关键作用。利用遗传方法在菌毛亚基通过外膜引导蛋白转运过程中捕获它们，提供了关于1型菌毛形成过程中亚基成分之间发生的结构相互作用的数据。对这些逐步组装中间体的电子显微镜和生化分析表明，菌毛亚基通过引导蛋白的中央通道线性转运，菌毛螺旋在细胞外形成。专门的菌毛蛋白亚基在这种多聚化以及粘附性菌毛的最终超微结构中都发挥着独特作用。
