Type IV Pilin Structures: Insights on Shared Architecture, Fiber Assembly, Receptor Binding and Type II Secretion

J Mol Microbiol Biotechnol. 2006;11(3-5):192-207. doi: 10.1159/000094054.


Type IV pili are long, flexible filaments that extend from the surface of Gram-negative bacteria and are formed by the polymerization of pilin subunits. This review focuses on the structural information available for each pilin subclass, type IVa and type IVb, highlighting the contributions crystal and nuclear magnetic resonance structures have made in understanding pilus function and assembly. In addition, the type II secretion pseudopilus subunit structure and helical assembly is compared to that of the type IV pilus. The pilin subunits adopt an alphabeta-roll fold formed by the hydrophobic packing of the C-terminal half of a long alpha-helix against an antiparallel beta-sheet. The conserved N-terminal half of the same alpha-helix, as well as two sequence- and structurally-variable regions, protrude from this globular head domain. Filament models have a hydrophobic core formed by the signature long alpha-helices, with variable regions at the filament surface.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / physiology
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / physiology
  • Fimbriae Proteins / chemistry
  • Fimbriae Proteins / physiology*
  • Fimbriae, Bacterial / chemistry
  • Fimbriae, Bacterial / physiology*
  • Molecular Sequence Data
  • Neisseria gonorrhoeae / physiology
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Pseudomonas aeruginosa / physiology
  • Salmonella typhi / physiology
  • Transcription Factors / chemistry
  • Transcription Factors / physiology
  • Vibrio cholerae / physiology


  • Bacterial Proteins
  • BfpA protein, E coli
  • Escherichia coli Proteins
  • TcpA protein, Vibrio cholerae
  • Transcription Factors
  • pilE protein, Neisseria gonorrhoeae
  • pilS protein, Bacteria
  • Fimbriae Proteins

Associated data

  • PDB/1DZO
  • PDB/1HPW
  • PDB/1OQV
  • PDB/1OQW
  • PDB/1Q5F
  • PDB/1QVE
  • PDB/1T92
  • PDB/1X6Z
  • PDB/1ZWT
  • PDB/2PIL