RecA-binding pilE G4 sequence essential for pilin antigenic variation forms monomeric and 5' end-stacked dimeric parallel G-quadruplexes

Structure. 2012 Dec 5;20(12):2090-102. doi: 10.1016/j.str.2012.09.013. Epub 2012 Oct 18.


Neisseria gonorrhoeae is an obligate human pathogen that can escape immune surveillance through antigenic variation of surface structures such as pili. A G-quadruplex-forming (G4) sequence (5'-G(3)TG(3)TTG(3)TG(3)) located upstream of the N. gonorrhoeae pilin expression locus (pilE) is necessary for initiation of pilin antigenic variation, a recombination-based, high-frequency, diversity-generation system. We have determined NMR-based structures of the all parallel-stranded monomeric and 5' end-stacked dimeric pilE G-quadruplexes in monovalent cation-containing solutions. We demonstrate that the three-layered all parallel-stranded monomeric pilE G-quadruplex containing single-residue double-chain reversal loops, which can be modeled without steric clashes into the 3 nt DNA-binding site of RecA, binds and promotes E. coli RecA-mediated strand exchange in vitro. We discuss how interactions between RecA and monomeric pilE G-quadruplex could facilitate the specialized recombination reactions leading to pilin diversification.

Publication types

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

MeSH terms

  • Antigens, Bacterial / chemistry
  • Antigens, Bacterial / genetics*
  • Base Pairing
  • Base Sequence
  • Binding Sites
  • DNA, Bacterial / chemistry*
  • Deuterium Exchange Measurement
  • Escherichia coli Proteins / chemistry*
  • Fimbriae Proteins / chemistry
  • Fimbriae Proteins / genetics*
  • G-Quadruplexes*
  • GC Rich Sequence
  • Immune Evasion
  • Models, Molecular
  • Neisseria gonorrhoeae / genetics*
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Binding
  • Rec A Recombinases / chemistry*


  • Antigens, Bacterial
  • DNA, Bacterial
  • Escherichia coli Proteins
  • Fimbriae Proteins
  • Rec A Recombinases

Associated data

  • PDB/2LXQ
  • PDB/2LXV