Adaptor function of PapF depends on donor strand exchange in P-pilus biogenesis of Escherichia coli

J Bacteriol. 2007 Jul;189(14):5276-83. doi: 10.1128/JB.01648-06. Epub 2007 May 11.


P-pilus biogenesis occurs via the highly conserved chaperone-usher pathway and involves the strict coordination of multiple subunit proteins. All nonadhesin structural P-pilus subunits possess the same topology, consisting of two domains: an incomplete immunoglobulin-like fold (pilin body) and an N-terminal extension. Pilus subunits form interactions with one another through donor strand exchange, occurring at the usher, in which the N-terminal extension of an incoming subunit completes the pilin body of the preceding subunit, allowing the incorporation of the subunit into the pilus fiber. In this study, pilus subunits in which the N-terminal extension was either deleted or swapped with that of another subunit were used to examine the role of each domain of PapF in functions involving donor strand exchange and hierarchical assembly. We found that the N-terminal extension of PapF is required to adapt the PapG adhesin to the tip of the fiber. The pilin body of PapF is required to efficiently initiate assembly of the remainder of the pilus, with the assistance of the N-terminal extension. Thus, distinct functions were assigned to each region of the PapF subunit. In conclusion, all pilin subunits possess the same overall architectural topology; however, each N-terminal extension and pilin body has specific functions in pilus biogenesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adhesins, Escherichia coli / genetics
  • Adhesins, Escherichia coli / metabolism*
  • Amino Acid Sequence
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli / ultrastructure
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Escherichia coli Proteins / physiology
  • Fimbriae Proteins / genetics
  • Fimbriae Proteins / metabolism*
  • Fimbriae Proteins / physiology
  • Fimbriae, Bacterial / genetics
  • Fimbriae, Bacterial / metabolism*
  • Fimbriae, Bacterial / physiology
  • Genetic Complementation Test
  • Immunoblotting
  • Microscopy, Electron
  • Models, Biological
  • Molecular Sequence Data
  • Mutation
  • Sequence Homology, Amino Acid


  • Adhesins, Escherichia coli
  • Escherichia coli Proteins
  • PapG protein, E coli
  • Fimbriae Proteins