Type IV Pilus Structure
from: Pili and Flagella: Current Research and Future Trends (Edited by: Ken Jarrell). Caister Academic Press, U.K. (2009)
The Type IV pili are architectural marvels of biology. These helical arrays of thousands of copies of a single pilin subunit are extremely thin and flexible yet remarkably strong, and they possess a diverse array of functions. Type IV pili are essential for host colonization and virulence for many Gram negative bacteria, and may also play a role in pathogenesis for some Gram positive bacteria. High resolution structures of pilin subunits have been determined by X-ray crystallography and nuclear magnetic resonance spectroscopy both as full length proteins and as soluble fragments. These structures have been used to generate computational models of pilus filament assemblies, guided by biophysical parameters extracted from fiber diffraction data and electron microscopy image analysis, and by a dense literature of biological data. Most recently, cryo-electron microscopy has provided an intermediate resolution structure of a pilus filament. The pilin structures and filament models have been instrumental in advancing our understanding of the molecular mechanisms driving pilus assembly and the role of Type IV pili in key bacterial functions such as immune evasion, microcolony formation and DNA uptake. In very general terms the structural data point to a shared subunit structure and filament architecture for all Type IV pili, but a comprehensive, atomic-level understanding of these filaments and their biological processes will require additional higher resolution filament structures as well as new structural, genetic and biochemical data on the many components of the pilus assembly apparatus read more ...