CHARACTERIZATION OF THE TYPE IV PILUS MOTOR COMPLEX

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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.