title: The unfolding of the P pili quaternary structure by stretching is reversible, not plastic.
abstract: P pili are protein filaments expressed by uropathogenic Escherichia coli that mediate binding to glycolipids on epithelial cell surfaces, which is a prerequisite for bacterial infection. When a bacterium, attached to a cell surface, is exposed to external forces, the pili, which are composed of approximately 10(3) PapA protein subunits arranged in a helical conformation, can elongate by unfolding to a linear conformation. This property is considered important for the ability of a bacterium to withstand shear forces caused by urine flow. It has hitherto been assumed that this elongation is plastic, thus constituting a permanent conformational deformation. We demonstrate, using optical tweezers, that this is not the case; the unfolding of the helical structure to a linear conformation is fully reversible. It is surmised that this reversibility helps the bacteria regain close contact to the host cells after exposure to significant shear forces, which is believed to facilitate their colonization.
authors.affiliation: Department of Physics, and Electronics, Umeå University, 901 87 Umeå, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Fällman
authors.forename: Staffan
authors.initials: S
authors.lastname: Schedin
authors.forename: Jana
authors.initials: J
authors.lastname: Jass
authors.forename: Bernt-Eric
authors.initials: BE
authors.lastname: Uhlin
authors.forename: Ove
authors.initials: O
authors.lastname: Axner
mesh_terms: D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D036781:Fimbriae Proteins / Q000737:chemistry / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D020836:Protein Structure, Quaternary
chemical_list: C078802:AtpA protein, E coli; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins