1. Exploring the 3D Molecular Architecture of Escherichia coli Type 1 Pili
- Author
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Peter Burkhard, Peter Sebbel, Rudi Glockshuber, Ueli Aebi, Marcus Häner, Uta Hermanns, Erik Hahn, Peter J. Wild, Nicole Taschner, and Shirley A. Müller
- Subjects
Microscopy, Electron, Scanning Transmission ,Models, Molecular ,Pilus assembly ,Macromolecular Substances ,Protein subunit ,Fimbria ,Bacterial Adhesion ,Pilus ,Bacterial Proteins ,Structural Biology ,Endopeptidases ,Scanning transmission electron microscopy ,Escherichia coli ,Image Processing, Computer-Assisted ,Humans ,Microscopy, Immunoelectron ,Molecular Biology ,Adhesins, Escherichia coli ,Virulence ,biology ,Chemistry ,Escherichia coli Proteins ,Resolution (electron density) ,biochemical phenomena, metabolism, and nutrition ,Protein Subunits ,Crystallography ,Fimbriae, Bacterial ,Pilin ,Helix ,biology.protein ,bacteria ,Fimbriae Proteins - Abstract
An integrated approach combining information gained by Fourier transformation, linear Markham superposition (real space) and mass-per-length measurement by scanning transmission electron microscopy was used to analyze the helical structure of the rod-like type 1 pili expressed by uropathogenic Escherichia coli strain W3110. The 3D reconstruction calculated from the experimental data showed the pili to be 6.9nm wide, right-handed helical tubes with a 19.31(+/-0.34)nm long helical repeat comprising 27 FimA monomers associated head-to-tail in eight turns of the genetic one-start helix. Adjacent turns of the genetic helix are connected via three binding sites making the pilus rod rather stiff. In situ immuno-electron microscopy experiments showed the minor subunit (FimH) mediating pilus adhesion to bladder epithelial cells to be the distal protein of the pilus tip, which had a spring-like appearance at higher magnification. The subunits FimG and FimF connect FimH to the FimA rod, the sequential orientation being FimA-FimF-FimG-FimH. The electron density map calculated at 18A resolution from an atomic model of the pilus rod (built using the pilin domain FimH together with the G1 strand of FimC as a template for FimA and applying the optimal helical parameters determined to the head-to-tail interaction model for pilus assembly) was practically identical with that of the actual 3D reconstruction.
- Published
- 2002