Structure and Assembly of the Enterohemorrhagic Escherichia coli Type 4 Pilus

Structure. 2019 Jul 2;27(7):1082-1093.e5. doi: 10.1016/j.str.2019.03.021. Epub 2019 May 2.


Bacterial type 4a pili are dynamic surface filaments that promote bacterial adherence, motility, and macromolecular transport. Their genes are highly conserved among enterobacteria and their expression in enterohemorrhagic Escherichia coli (EHEC) promotes adhesion to intestinal epithelia and pro-inflammatory signaling. To define the molecular basis of EHEC pilus assembly, we determined the structure of the periplasmic domain of its major subunit PpdD (PpdDp), a prototype of an enterobacterial pilin subfamily containing two disulfide bonds. The structure of PpdDp, determined by NMR, was then docked into the density envelope of purified EHEC pili obtained by cryoelectron microscopy (cryo-EM). Cryo-EM reconstruction of EHEC pili at ∼8 Å resolution revealed extremely high pilus flexibility correlating with a large extended region of the pilin stem. Systematic mutagenesis combined with functional and interaction analyses identified charged residues essential for pilus assembly. Structural information on exposed regions and interfaces between EHEC pilins is relevant for vaccine and drug discovery.

Keywords: EHEC; Escherichia coli; NMR; cryo-EM; hemorrhagic coli pilus (HCP); molecular modeling; pilin structure; pilus assembly; type 4 pili; type II secretion system.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Cloning, Molecular
  • Cryoelectron Microscopy
  • Enterohemorrhagic Escherichia coli / chemistry*
  • Enterohemorrhagic Escherichia coli / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Fimbriae Proteins / chemistry*
  • Fimbriae Proteins / genetics
  • Fimbriae Proteins / metabolism
  • Fimbriae, Bacterial / chemistry
  • Fimbriae, Bacterial / metabolism
  • Fimbriae, Bacterial / ultrastructure*
  • Gene Expression
  • Genetic Vectors / chemistry
  • Genetic Vectors / metabolism
  • Kinetics
  • Molecular Docking Simulation
  • Mutation
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Static Electricity
  • Thermodynamics


  • Escherichia coli Proteins
  • PpdD protein, E coli
  • Recombinant Proteins
  • Fimbriae Proteins