title: Dynamic restacking of Escherichia coli P-pili.
abstract: P-pili of uropathogenic Escherichia coli mediate the attachment to epithelial cells in the human urinary tract and kidney and therefore play an important role in infection. A better understanding of this mechanism could help to prevent bacteria from spreading but also provides interesting insights into molecular mechanics for future nanotech applications. The helical rod design of P-pili provides an efficient design to withstand hydrodynamic shear forces. The adhesive PapG unit at the distal end of the P-pilus forms a specific bond with the glycolipid Galabiose. This bond has a potential width Deltax = 0.7 +/- 0.15 nm and a dissociation rate K (Off) = 8.0.10(-4) +/- 5.0.10(-4) s(-1). It withstands a force of approximately 49 pN under physiological conditions. Additionally, we analyzed the behavior of unstacking and restacking of the P-pilus with dynamic force spectroscopy at velocities between 200 and 7,000 nm/s. Up to a critical extension of 66% of the totally stretched P-pilus, un/re-stacking was found to be fully reversible at velocities up to 200 nm/s. If the P-pilus is stretched beyond this critical extension a characteristic hysteresis appears upon restacking. This hysteresis originates from a nucleation process comparable to a first-order phase transition in an undercooled liquid. Analysis of the measurement data suggests that 20 PapA monomers are involved in the formation of a nucleation kernel.
authors.affiliation: Lehrstuhl für Angewandte Physik and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstrasse 54, 80799, Munich, Germany. Lugmaier@lmu.de
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lugmaier
authors.forename: Staffan
authors.initials: S
authors.lastname: Schedin
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Kühner
authors.forename: Martin
authors.initials: M
authors.lastname: Benoit
mesh_terms: D018830:Adhesins, Escherichia coli / Q000378:metabolism; D004187:Disaccharides / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D009010:Monte Carlo Method; D013379:Substrate Specificity
chemical_list: D018830:Adhesins, Escherichia coli; D004187:Disaccharides; C092426:PapG protein, E coli; C032103:4-O-alpha-D-galactopyranosyl-D-galactose; D036781:Fimbriae Proteins