title: Dynamic force spectroscopy of E. coli P pili.
abstract: Surface organelles (so-called pili) expressed on the bacterial membrane mediate the adhesion of Escherichia coli causing urinary tract infection. These pili possess some extraordinary elongation properties that are assumed to allow a close bacterium-to-host contact even in the presence of shear forces caused by urine flow. The elongation properties of P pili have therefore been assessed for low elongation speeds (steady-state conditions). This work reports on the behavior of P pili probed by dynamic force spectroscopy. A kinetic model for the unfolding of a helixlike chain structure is derived and verified. It is shown that the unfolding of the quaternary structure of the PapA rod takes place at a constant force that is almost independent of elongation speed for slow elongations (up to approximately 0.4 mum/s), whereas it shows a dynamic response with a logarithmic dependence for fast elongations. The results provide information about the energy landscape and reaction rates. The bond length and thermal bond opening and closure rates for the layer-to-layer bond have been assessed to approximately 0.76 nm, approximately 0.8 Hz, and approximately 8 GHz, respectively. The results also support a previously constructed sticky-chain model for elongation of the PapA rod that until now had been experimentally verified only under steady-state conditions.
authors.affiliation: Department of Physics and Department of Molecular Biology, Umeå University, Umeå, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
authors.forename: Erik
authors.initials: E
authors.lastname: Fällman
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
authors.forename: Ove
authors.initials: O
authors.lastname: Axner
mesh_terms: D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000502:physiology*; D036781:Fimbriae Proteins / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000502:physiology*; D008954:Models, Biological; D017510:Protein Folding; D033081:Shear Strength
chemical_list: C078802:AtpA protein, E coli; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins