title: Unfolding and refolding properties of S pili on extraintestinal pathogenic Escherichia coli.
abstract: S pili are members of the chaperone-usher-pathway-assembled pili family that are predominantly associated with neonatal meningitis (S(II)) and believed to play a role in ascending urinary tract infections (S(I)). We used force-measuring optical tweezers to characterize the intrinsic biomechanical properties and kinetics of S(II) and S(I) pili. Under steady-state conditions, a sequential unfolding of the layers in the helix-like rod occurred at somewhat different forces, 26 pN for S(II) pili and 21 pN for S(I) pili, and there was an apparent difference in the kinetics, 1.3 and 8.8 Hz. Tests with bacteria defective in a newly recognized sfa gene (sfaX (II)) indicated that absence of the sfaX (II) gene weakens the interactions of the fimbrium slightly and decreases the kinetics. Data of S(I) are compared with those of previously assessed pili primary associated with urinary tract infections, the P and type 1 pili. S pili have weaker layer-to-layer bonds than both P and type 1 pili, 21, 28 and 30 pN, respectively. In addition, the S pili kinetics are ~10 times faster than the kinetics of P pili and ~550 times faster than the kinetics of type 1 pili. Our results also show that the biomechanical properties of pili expressed ectopically from a plasmid in a laboratory strain (HB101) and pili expressed from the chromosome of a clinical isolate (IHE3034) are identical. Moreover, we demonstrate that it is possible to distinguish, by analyzing force-extension data, the different types of pili expressed by an individual cell of a clinical bacterial isolate.
authors.affiliation: Department of Physics, Umeå University, 901 87, Umea, Sweden.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Castelain
authors.forename: Annika E
authors.initials: AE
authors.lastname: Sjöström
authors.forename: Erik
authors.initials: E
authors.lastname: Fällman
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000737:chemistry* / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000235:genetics; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D009154:Mutation; D052898:Optical Tweezers; D010957:Plasmids / Q000235:genetics; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013057:Spectrum Analysis
chemical_list: D029968:Escherichia coli Proteins; D020033:Protein Isoforms; C101637:ymcE protein, E coli; D036781:Fimbriae Proteins