CHARACTERIZATION OF THE TYPE IV PILUS MOTOR COMPLEX

IV型菌毛是长而细的细丝，显示在许多细菌的表面。它们具有多种功能，这些功能依赖于它们(i)粘附各种底物的能力，包括宿主细胞表面、附近细菌的菌毛、DNA和噬菌体，以及（ii）解聚合或缩回，这将细菌沿着粘膜表面拉紧，将它们拉紧在一起形成保护性聚集体，并将DNA和噬菌体等底物吸引到细菌中进行营养和遗传变异。IV型菌毛是由数千个主要菌毛亚基的拷贝组成的聚合物。菌毛是由一个复杂的分子机器从细胞质跨越细菌包膜到外膜组装在细胞膜上的。我们的实验室处于这一领域的前沿，我们的IV型菌毛蛋白亚基的x射线晶体结构和完整菌毛细丝的低温电子显微镜重建提供了这些细胞器的原子分辨率图片和理解细丝组装的框架。许多研究小组在了解毛组装装置的结构方面取得了显著进展，但这些毛组装的机制仍然是一个谜。本提案旨在表征毛丝机械中的分子马达复合物，以揭示它如何驱动灯丝组装。

Type IV pili are long thin filaments displayed on the surfaces of many bacteria. They have a diverse array of functions that rely on their ability to (i) adhere to various substrates, including host cell surfaces, pili from nearby bacteria, DNA and bacteriophage, and (ii) to depolymerize or retract, which pulls the bacteria along mucosal surfaces, pulls them close together in protective aggregates, and can draw substrates like DNA and phage into the bacterium for nutrition and genetic variation. Type IV pili are polymers of thousands of copies of the major pilin subunit. The pili are assembled at the inner membrane by a complex molecular machine spanning the bacterial envelope from the cytoplasm to the outer membrane. Our lab is at the forefront of this field, with our x-ray crystal structures of Type IV pilin subunits and cryo-electron microscopy reconstructions of intact pilus filaments providing an atomic resolution picture of these organelles and a framework for understanding filament assembly. Remarkable progress has been made by many groups in understanding the architecture of the pilus assembly apparatus, yet the mechanism by which these pili are assembled remains a mystery. This proposal aims to characterize the molecular motor complex within the pilus machinery to reveal how it drives filament assembly.